/in/foo.cc: In function 'int main()':
/in/foo.cc:46:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v1.size();i++){
               ~^~~~~~~~~~
/in/foo.cc:50:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v1.size();i++){
               ~^~~~~~~~~~
/in/foo.cc:66:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<v2.size();i++){
                ~^~~~~~~~~~
/in/foo.cc:69:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<v1.size();i++){
                ~^~~~~~~~~~
/in/foo.cc:77:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<v1.size();i++){
                ~^~~~~~~~~~