/in/foo.cc: In function 'int main()':
/in/foo.cc:10:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if((t=s.find(s1))==string::npos){
                    ^
/in/foo.cc:15:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while((t=s.find(s1,t+s1.size()))!=string::npos){
                                   ^