/in/foo.cc: In function 'int main()':
/in/foo.cc:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if((t=s.find(s1,t))==string::npos){
                       ^
/in/foo.cc:20:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    while((t=s.find(s1,t+s1.size()))!=string::npos){
                                    ^