/in/foo.cc: In function 'int main()':
/in/foo.cc:7:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.size();)
                 ~^~~~~~~~~
/in/foo.cc:10:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=i;j<i+s1.size() ;j++)
                     ~^~~~~~~~~~~~
/in/foo.cc:16:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int k=0;k<s2.size();k++)cout<<s2[k];
                         ~^~~~~~~~~~