Some testcases contain empty strings, which is very nasty, and they should be read in combination with scanf and gets. I had scanf("%d\n", &N) initially, which skipped the empty lines afterwards, so my gets() calls where kind of useless.

Secondly, here are some testcases:

2
bc
abcd
1
abcx

Should return 1 2

2
bc
abcd
1
abcd

Should return 1 1