/in/foo.cc: In function 'bool check(int, int, int)':
/in/foo.cc:16:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(t=1;t<W[i].length();++t)
             ~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:38:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(S[j].find(W[i][0])!=-1)
                ~~~~~~~~~~~~~~~~~~^~~~