View Compilation Error

0_0_8813432_1293.cpp: In function `int dfs(int)':
0_0_8813432_1293.cpp:26: error: `k' undeclared (first use this function)
0_0_8813432_1293.cpp:26: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8813432_1293.cpp:27: error: `res' undeclared (first use this function)