View Compilation Error

0_0_10284354_23120.cpp: In function `void DFS(int, int, int)':
0_0_10284354_23120.cpp:15: error: `abs' undeclared (first use this function)
0_0_10284354_23120.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10284354_23120.cpp: In function `int main()':
0_0_10284354_23120.cpp:53: error: `abs' undeclared (first use this function)