/in/foo.cc: In function 'int main()':
/in/foo.cc:19:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v.size();i++){
               ~^~~~~~~~~
/in/foo.cc:32:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v.size();i++){
               ~^~~~~~~~~
/in/foo.cc:44:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<v.size();j++){
               ~^~~~~~~~~