/in/foo.cc: In function 'bool check(int, int)':
/in/foo.cc:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int t = 0; t < vi.size(); t++)
                     ~~^~~~~~~~~~~
/in/foo.cc: In function 'void print()':
/in/foo.cc:67:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < vi.size(); i++)
                     ~~^~~~~~~~~~~
/in/foo.cc:69:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < vi[0].size(); j++)
                         ~~^~~~~~~~~~~~~~