How GNU compiler differentiates between " %c" and "%s" in C

In the recent contest (LTIME62B) I made a brute force solution to solve FRCPRT for 30 points. I submitted my solution 2 times. Only difference I made was in the former one I was scanning the input by "%s" (i.e. as a whole string) and in the latter one I was scanning it by "%c". I got WA in the former one but AC for latter one. Can anyone explain me why I got WA with "%s"?

WA SolutionAC Solution