/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() ;i++)
                 ~^~~~~~~~~
/in/foo.cc:9:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s1.size() ;i++)
                 ~^~~~~~~~~~
/in/foo.cc:11:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=1;i<=max(s.size() ,s1.size() );i++)
                 ~^~~~~~~~~~~~~~~~~~~~~~~~~~~