/in/foo.cc: In function 'int main()':
/in/foo.cc:16:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < data.size(); i++)
                     ^
/in/foo.cc:23:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < ans.size(); i++)
                    ^