View Compilation Error

0_0_8837636_25816.cpp: In function `bool dfs(int)':
0_0_8837636_25816.cpp:36: error: `u' undeclared (first use this function)
0_0_8837636_25816.cpp:36: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8837636_25816.cpp:36: error: `v' undeclared (first use this function)