foo.cc: In function 'void DFS(int&, int, int, int)':
foo.cc:32:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = now_cake; i < cake.size(); i++)
                           ~~^~~~~~~~~~~~~
foo.cc:53:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 0; i < cake.size(); i++)
                    ~~^~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:101:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int rr = 0; rr < mouth.size(); rr++)
                   ~~~^~~~~~~~~~~~~~
foo.cc:98:6: warning: unused variable 'max' [-Wunused-variable]
  int max = 0;
      ^~~