C99 7.12.7.3 (page 228) specifies the hypot functions. But I suspect that there is something wrong with them here. When I call hypot() to calculate the distance I got WA. But if adding this fragment of code:
double dist(double x, double y) { return sqrt(x * x + y * y); }
and call dist() instead of hypot() I got AC. Seems the C Compiler is not compatible with C99. I hope the administrators can update their C compiler.