40分蒟蒻求助

2，3，4测试点WA

以下是代码

#include <bits/stdc++.h>
using namespace std;
int main()
{
	long long n, m, hn = 0, hbn = 0, sumn = 0,sumbn=0;
	double avern = 0, averbn = 0;
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		if (i % m == 0)
		{
			hn += i;
			sumn++;
		}
		if (i % m != 0)
		{
			hbn += i;
			sumbn++;
		}
	}
	avern = hn / sumn;
	averbn = hbn / sumbn;
	printf("%.1lf %.1lf", avern, averbn);
	return 0;
}

求助各位大佬