蒟蒻求助，为什莫全错？

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,k;
    double sum;
    cin >> n >> k;
    for (int i = k; i <= n; i += k) sum += i;
    cout << setiosflags(ios::fixed);
    cout << setprecision(1) << sum / (n / k);
    sum = (1 + n) * n / 2 - sum;
    cout << setiosflags(ios::fixed);
    cout << setprecision(1) << sum / (n - n / k);
    return 0;
}