/in/foo.cc: In function 'bool check(int, int)':
/in/foo.cc:13:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<sen[p].size(); i++)
                  ~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:79:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<sen.size(); i++)
                  ~^~~~~~~~~~~
/in/foo.cc:100:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<sen.size(); i++)
                  ~^~~~~~~~~~~