View Compilation Error

0_0_10979395_31857.cpp: In function `int main()':
0_0_10979395_31857.cpp:48: error: `b' undeclared (first use this function)
0_0_10979395_31857.cpp:48: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10979395_31857.cpp:48: error: expected `;' before "dfs"