/in/foo.cc: In function 'int check(int, int)':
/in/foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s[x].size();i++){
              ~^~~~~~~~~~~~
/in/foo.cc:18:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=i;j<s[x].size();j++){
               ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:48:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
        for(int p=chong;p<s[k].size();p++) t+=s[k][p];
                        ~^~~~~~~~~~~~