diff --git a/2019/day22.py b/2019/day22.py
index 75def3e..890d53d 100644
--- a/2019/day22.py
+++ b/2019/day22.py
@@ -1,37 +1,168 @@
 EX1 = [
+    "deal with increment 7",
+    "deal into new stack",
+    "deal into new stack",
+]
+EX2 = [
     "cut 6",
     "deal with increment 7",
     "deal into new stack",
 ]
-
+EX3 = [
+    "deal with increment 7",
+    "deal with increment 9",
+    "cut -2",
+]
+EX4 = [
+    "deal into new stack",
+    "cut -2",
+    "deal with increment 7",
+    "cut 8",
+    "cut -4",
+    "deal with increment 7",
+    "cut 3",
+    "deal with increment 9",
+    "deal with increment 3",
+    "cut -1",
+]
 
 def main():
     with open("day22.txt") as input_file:
         lines = [l.rstrip() for l in input_file.readlines()]
 
-    deck = list(range(10007))
-    for line in lines:
+    # Part 1
+    deck = list(range(10))
+    # deck = list(range(10007))
+    deck = part1(deck, EX3)
+    print(deck)
+    # deck = part1(deck, lines)
+    # print(f"Position of card 2019: {deck.index(2019)}.")
+
+    # Part 2
+    part2(10, 1, EX3, pos=0); input()
+    part2(10, 1, EX3, pos=1); input()
+    part2(10, 1, EX3, pos=2); input()
+    part2(10, 1, EX3, pos=3); input()
+    part2(10, 1, EX3, pos=4); input()
+    part2(10, 1, EX3, pos=5); input()
+    part2(10, 1, EX3, pos=6); input()
+    part2(10, 1, EX3, pos=7); input()
+    part2(10, 1, EX3, pos=8); input()
+    part2(10, 1, EX3, pos=9); input()
+    # part2(10007, 1, lines, pos=8191)
+    # part2(119315717514047, 101741582076661, lines)
+    # print(f"2020th card: {deck[2020]}.")
+
+def part1(deck, commands):
+    for command in commands:
         # Deal into new stack.
-        if line.endswith("k"):
+        if command.endswith("k"):
             deck.reverse()
             continue
-
-        arg = int(line[line.rfind(" "):])
-
+        arg = int(command[command.rfind(" "):])
         # Deal with increment.
-        if line[0] == "d":
+        if command[0] == "d":
             new_deck = [None] * len(deck)
             for i in range(len(deck)):
                 new_deck[(i * arg) % len(new_deck)] = deck[i]
             deck = new_deck
-
         # Cut.
-        elif line[0] == "c":
+        elif command[0] == "c":
             cut, deck = deck[:arg], deck[arg:]
             deck += cut
+    return deck
 
-    print(f"Position of card 2019: {deck.index(2019)}.")
+def part2(deck_len, num_shuf, commands, pos=2020):
+    required = find_required(deck_len, commands, pos)
+    for c, r in zip(commands, required):
+        print(f"- Command '{c}' requires knowing value at {r[0]} for {r[1]}.")
+    print(f"Which gives us value at {pos}.")
+    deck = {i: i for r in required for i in r}
+    print(required)
+    print("Shuffling...")
+    shuffle(deck, required)
+    print(f"Card at {pos}: {deck[pos]}.")
+
+def find_required(deck_len, commands, pos):
+    required = []
+    for command in reversed(commands):
+        dest = pos
+        if command.endswith("k"):
+            pos = req_dins(pos, deck_len)
+            required.append((pos, dest))
+            continue
+        arg = int(command[command.rfind(" "):])
+        if command[0] == "d":
+            print(f"What's req for {pos} in deal with increment {arg}?")
+            pos = req_dwi(pos, deck_len, arg)
+            print(f"- answer: {pos}.")
+        elif command[0] == "c":
+            pos = req_cut(pos, deck_len, arg)
+        required.append((pos, dest))
+    required.reverse()
+    return required
+
+def req_dins(pos, deck_len):
+    return deck_len - 1 - pos
+
+def req_cut(pos, deck_len, n):
+    return (pos + n) % deck_len
+
+def req_dwi(pos, deck_len, inc):
+    # Straight is (i * arg) % deck_len = j
+    # (i * arg) = modinv(j, deck_len)
+    # i = modinv(j, deck_len) / arg
+    # damn idk
+    return (pos * inc - deck_len) % deck_len
+
+def shuffle(deck, required):
+    for required_pair in required:
+        from_pos, to_pos = required_pair
+        deck[to_pos] = deck[from_pos]
+
+def dins(parameter_list):
+    pass
+
+def cut(parameter_list):
+    pass
+
+def dwi(parameter_list):
+    pass
 
 
 if __name__ == "__main__":
-    main()
+    # main()
+
+    assert req_cut(0, 10, 3) == 3
+    assert req_cut(1, 10, 3) == 4
+    assert req_cut(2, 10, 3) == 5
+    assert req_cut(5, 10, 3) == 8
+    assert req_cut(8, 10, 3) == 1
+    assert req_cut(0, 10, -4) == 6
+    assert req_cut(0, 10, -4) == 6
+    assert req_cut(1, 10, -4) == 7
+    assert req_cut(2, 10, -4) == 8
+    assert req_cut(3, 10, -4) == 9
+    assert req_cut(4, 10, -4) == 0
+    assert req_cut(5, 10, -4) == 1
+    assert req_cut(6, 10, -4) == 2
+    assert req_cut(7, 10, -4) == 3
+    assert req_cut(8, 10, -4) == 4
+    assert req_cut(9, 10, -4) == 5
+
+    assert req_dins(0, 10) == 9
+    assert req_dins(1, 10) == 8
+    assert req_dins(2, 10) == 7
+    assert req_dins(8, 10) == 1
+    assert req_dins(9, 10) == 0
+
+    assert req_dwi(0, 10, 3) == 0
+    assert req_dwi(1, 10, 3) == 7
+    assert req_dwi(2, 10, 3) == 4
+    assert req_dwi(3, 10, 3) == 1
+    assert req_dwi(4, 10, 3) == 8
+    assert req_dwi(5, 10, 3) == 5
+    assert req_dwi(6, 10, 3) == 2
+    assert req_dwi(7, 10, 3) == 9
+    assert req_dwi(8, 10, 3) == 6
+    assert req_dwi(9, 10, 3) == 3