/in/foo.cc: In function 'int main()':
/in/foo.cc:9:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(a.size()<k){
        ~~~~~~~~^~
/in/foo.cc:19:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();i++){
              ~^~~~~~~~~
/in/foo.cc:29:9: warning: statement has no effect [-Wunused-value]
   for(it;it!=g.end();it++){
         ^