View Compilation Error

0_0_6820999_28432.cpp: In function `double dis(Point, Point)':
0_0_6820999_28432.cpp:22: error: `sqrt' undeclared (first use this function)
0_0_6820999_28432.cpp:22: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6820999_28432.cpp: In function `double closest_dis(int, int)':
0_0_6820999_28432.cpp:33: error: `fabs' undeclared (first use this function)