/in/foo.cc: In function 'int main()':
/in/foo.cc:26:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<=s1.size()-1;++i){
                ^
/in/foo.cc:29:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(j=1;j<=s2.size()-1;++j){
              ^
/in/foo.cc:34:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(j==s2.size()){
         ^