/in/foo.cc: In function 'int main()':
/in/foo.cc:43:24: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
         planet[x-1][y] -= check( planet[x-1][y-1] );
         ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:47:46: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
             planet[x-1][y] -= check( planet[x-2][y] );
                                             ~^~