n is 1 n is 2 n mod 100 is 1 n mod 100 is 2 n mod 100 in 3..4 n mod 10 is 1 n mod 10 is 2 n mod 10 in 3..4 n is 1 n is 2 n is 11 n is 12 n in 3..10 or n in 13..19 n is 1