Hello everyone, can anybody help me with this problem : https://vjudge.net/problem/HDU-1115

After searching on gg in the afternoon, I found around to solve this: https://math.stackexchange.com/questions/90463/how-can-i-calculate-the-centroid-of-polygon.

But after submitting, I don't know why I get the wrong answer, I think I can have some errors with my Complex struct, but I'm not sure, please help me. Thank you!

This is my code : https://codeforces.net/contest/119/submission/189358165

Sorry my English is not good.