/in/foo.cc: In function 'int main()':
/in/foo.cc:35:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<d.size();i++) {
               ~^~~~~~~~~
/in/foo.cc:40:21: warning: left operand of comma operator has no effect [-Wunused-value]
    for(int j=0,k=0;j<s1,k<s2;j++,k++) {
                    ~^~~