diff --git a/2020/16.py b/2020/16.py
new file mode 100755
index 0000000..7d31e3f
--- /dev/null
+++ b/2020/16.py
@@ -0,0 +1,358 @@
+#!/usr/bin/env python
+
+from aoc import get_input # AoC
+import re # regex
+
+data = get_input(16).strip()
+
+stuff = data.split("\n\n")
+
+params = stuff[0].split("\n")
+myticket = stuff[1].split("\n")[1]
+tickets = stuff[2].split("\n")
+tickets.pop(0)
+
+
+def parseParam(param):
+    name, rnga1, rnga2, rngb1, rngb2 = re.match(r"([a-z\ ]+): ([0-9]+)-([0-9]+) or ([0-9]+)-([0-9]+)", param).groups()
+
+    rng1 = range(int(rnga1), int(rnga2) + 1)
+    rng2 = range(int(rngb1), int(rngb2) + 1)
+
+    return name, rng1, rng2
+
+ranges = dict()
+for i in range(len(params)):
+    par = params[i]
+    name, rng1, rng2 = parseParam(par)
+    ranges[name] = (rng1, rng2)
+
+
+def parseTicket(ticket):
+    return [int(n) for n in ticket.split(",")]
+
+badvals = []
+
+goodtickets = [ti  for ti in tickets]
+badtickets = []
+
+for i in range(len(tickets)):
+    if( i > 0 ):
+        ticket = tickets[i]
+        vals = parseTicket(ticket)
+
+        for v in vals:
+            checks = []
+            for cl, rng in ranges.items():
+                for r in rng:
+                    checks.append( v in r )
+
+            valid = any(check  for check in checks)
+
+            if(not valid):
+                badvals.append(v)
+                break
+
+        if( not valid ):
+            print(f"Bad: {ticket=} {any(checks)=}")
+            goodtickets.remove(ticket)
+            badtickets.append(ticket)
+
+
+print("\nPart1:", sum(badvals))
+
+# freeranges = ranges
+
+# def getClass(num):
+#     out = None
+#     for cl, rng in freeranges.items():
+#         check1 = num in rng[0]
+#         check2 = num in rng[1]
+#         check = check1 or check2
+
+#         if(check):
+#             freeranges.pop(cl, None)
+#             out = cl
+
+#             break
+#         else:
+#             continue
+
+#     return out
+
+# def getClass2(num):
+#     out = None
+#     for cl, rng in ranges.items():
+#         check1 = num in rng[0]
+#         check2 = num in rng[1]
+#         check = check1 or check2
+
+#         if(check):
+#             out = cl
+
+#             break
+#         else:
+#             continue
+
+#     return out
+
+# print( getClass(3) )
+# print( getClass(9) )
+# print( getClass(18) )
+# print("\n\n\n")
+
+import itertools
+import operator
+
+def most_common(L):
+    SL = sorted((x, i) for i, x in enumerate(L))
+    groups = itertools.groupby(SL, key=operator.itemgetter(0))
+    def _auxfun(g):
+        item, iterable = g
+        count = 0
+        min_index = len(L)
+        for _, where in iterable:
+            count += 1
+            min_index = min(min_index, where)
+        return count, -min_index
+    return max(groups, key=_auxfun)[0]
+
+seenindex = []
+classIndex = dict()
+
+#goodtickets.insert( 0, myticket )
+print("####", len(goodtickets), "/" , len(tickets), "valid")
+
+goodtickets = [ parseTicket(t)  for t in goodtickets ]
+
+
+def possibleParams(num):
+    possible = []
+    for cl, rng in ranges.items():
+        check1 = num in rng[0]
+        check2 = num in rng[1]
+        check = check1 or check2
+
+        if(check):
+            print(f"POSSIBLE {num=} {cl=}")
+            possible.append(cl)
+
+    return possible
+
+from collections import defaultdict as dd
+
+probIndex = dd(dict)
+
+#print("22222", goodtickets[0])
+
+
+# go through each param
+# get possible indexs
+# take least from possible
+# add index to seen
+
+print(params)
+
+# for param, rng in ranges.items():
+#     print("\nchecking param", param)
+#     possible = {
+#         0: 0,
+#         1: 0,
+#         2: 0,
+#         3: 0,
+#         4: 0,
+#         5: 0,
+#         6: 0,
+#         7: 0,
+#         8: 0,
+#         9: 0,
+#         10: 0,
+#         11: 0,
+#         12: 0,
+#         13: 0,
+#         14: 0,
+#         15: 0,
+#         16: 0,
+#         17: 0,
+#         18: 0,
+#         19: 0
+#     }
+
+#     for ticket in tickets:
+#         for i in range(len(parseTicket(ticket))):
+#             n = parseTicket(ticket)[i]
+
+#             checks = []
+#             for r in rng:
+#                 checks.append( n in r )
+
+#             valid = any(check  for check in checks)
+
+#             print(f"Possible {rng=} {n=} {i=} {param=}", end="")
+
+#             if(valid):
+#                 print(" +1")
+#                 possible[i] += 1
+#             else:
+#                 print("")
+
+#     probIndex[param] = possible
+
+def numIsValid(num, rng):
+    checks = []
+    for r in rng:
+        checks.append( num in r )
+
+    valid = any(check  for check in checks)
+    return valid
+
+
+for i in range( len(goodtickets[0]) ):
+    validcls = []
+
+    for ticket in goodtickets:
+        num = ticket[i]
+
+        for cl, rng in ranges.items():
+            valid = numIsValid(num, rng)
+
+            if(valid):
+                validcls.append(cl)
+
+    probIndex[i] = validcls
+
+    
+seenIndex = []
+seenValid = []
+paramPos = dict()
+print("\n\nTHING")
+
+for chari in range( len(goodtickets[0]) ):
+    if( not chari in seenIndex ):
+        valids = probIndex[chari]
+
+        least = 99999999
+        leastparam = None
+        for v in valids:
+            if( valids.count(v) < least and not v in seenValid ):
+                least = valids.count(v)
+                leastparam = v
+
+        print(f"{least=} {leastparam=} {valids=}")
+
+        paramPos[chari] = leastparam
+
+        seenIndex.append(chari)
+        seenValid.append(leastparam)
+
+print(paramPos)
+
+
+# for param, pos in probIndex.items():
+#     if(param in seen):
+#         continue
+
+#     print("\n", param)
+
+#     for i, val in probIndex[param].items():
+#         print(i, val)
+
+
+print(paramPos)
+
+# for i in range(len(goodtickets[0])):
+#     posParams = [ possibleParams( goodtickets[0][i] ) ]
+
+#     for j in range(1, len(goodtickets)):
+#         tick = goodtickets[j]
+#         n = tick[i]
+#         pos = possibleParams( n )
+
+#         posParams.append(pos)
+
+#     probIndex[i] = posParams
+
+
+# print(len(probIndex[19]))
+
+# def checkParamForIndex(i, p):
+#     params = probIndex[i]
+#     # check = all( p in ticket  for ticket in params )
+#     # print("###############", check, len(params))
+
+
+
+
+# for i in range(len(goodtickets[0])):
+#     num = goodtickets[0][i]
+#     numcl = [ getClass(num) ]
+
+#     for j in range(0, len(goodtickets)):
+#         tick = goodtickets[j]
+#         n = tick[i]
+#         nclass = getClass2(n)
+#         if(nclass):
+#             numcl.append(nclass)
+
+#     common = most_common(numcl)
+#     same_count = numcl.count(common)
+#     r = (same_count / len(goodtickets)) * 100
+#     print(f"{i=} {num=} {common=} {same_count=} {r=}% {numcl[0]=}")
+#     probIndex[common][i] = r
+
+# print(probIndex)
+
+# paramIndex = dict()
+
+# for parameter, probs in probIndex.items():
+#     lastProb = 0
+#     bestIndex = None
+#     for i, prob in probs.items():
+#         if( prob > lastProb ):
+#             lastProb = prob
+#             bestIndex = i
+
+#     paramIndex[parameter] = bestIndex
+
+# print("######", paramIndex)
+
+
+# for ticket in tickets:
+#     if( ticket in badtickets ):
+#         continue
+#     #print(ticket)
+
+#     p = parseTicket(ticket)
+
+#     for i in range(len(p)):
+#         check = not i in seenindex
+
+#         if( check ):
+
+#             num = p[i]
+#             cl = getClass(num)
+#             classIndex[cl] = i
+#             seenindex.append(i)
+
+#             continue
+
+
+myticket = parseTicket(myticket)
+thenums = []
+
+# for cl, i in paramIndex.items():
+#     if( "departure" in cl ):
+#         thenums.append( myticket[i] )
+
+print(thenums)
+
+import math
+
+print("  1409959524847 !=")
+print("#",math.prod(thenums))
+print("  21095351239483")
+print("  30145908219919 reverse")
+
+print(sum(thenums))
+
+print(classIndex)