/in/foo.cc: In function 'bool better(int, int, std::vector<std::vector<int> >&)':
/in/foo.cc:9:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (a == arr.size()-1)
      ~~^~~~~~~~~~~~~~~
/in/foo.cc:11:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (b==arr[0].size()-1)
      ~^~~~~~~~~~~~~~~~~
/in/foo.cc:14:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (b + 1 == arr[0].size() - 1)
       ~~~~~~^~~~~~~~~~~~~~~~~~~~
/in/foo.cc:19:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (a + 1 == arr.size() - 1)
      ~~~~~~^~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int caozuo(std::vector<std::vector<int> >&)':
/in/foo.cc:32:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (i != arr.size()-1 && j != arr[0].size()-1)
         ~~^~~~~~~~~~~~~~~
/in/foo.cc:32:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (i != arr.size()-1 && j != arr[0].size()-1)
                              ~~^~~~~~~~~~~~~~~~~~
/in/foo.cc:50:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i == arr.size() - 1)
        ~~^~~~~~~~~~~~~~~~~
/in/foo.cc:56:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    else if (j == arr[0].size() - 1)
             ~~^~~~~~~~~~~~~~~~~~~~