Crypt Map

No cheating!

1 -> 2; 2 -> 1; 3 -> 4; 4 -> 3; 5 -> 6; 6 -> 5; 7 -> 8; 8 -> 7; 9 -> 10; 10 -> 9; 11 -> 16; 12 -> 17; 13 -> 15; 14 -> 15; 15 -> 13; 16 -> 14; 17 -> 12; 18 -> 5; 19 -> 20; 20 -> 4;