View Compilation Error

0_0_9100411_100.cpp: In function `int dfs(int, int, int, int)':
0_0_9100411_100.cpp:17: error: `tx' undeclared (first use this function)
0_0_9100411_100.cpp:17: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9100411_100.cpp:17: error: `ty' undeclared (first use this function)