/in/foo.cc: In function 'void insert(int)':
/in/foo.cc:11:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int k=0;k<v[y].size();k++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'int lookup(int)':
/in/foo.cc:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int k=0;k<v[y].size();k++)
              ~^~~~~~~~~~~~