View Compilation Error

0_0_7685694_24804.cpp: In function `void dfs(node, int)':
0_0_7685694_24804.cpp:31: error: `abs' undeclared (first use this function)
0_0_7685694_24804.cpp:31: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7685694_24804.cpp: In function `int main()':
0_0_7685694_24804.cpp:54: error: `cin' undeclared (first use this function)