这一题答案能对，却是零分。都快疯了！

#include<bits/stdc++.h> 
using namespace std;
int main()
{
    double a1,b1,c,d;
    int n1,k,n,n2,k1,b=0,a=0;
    cin>>n>>k;
    k1=k;
    for (n1=1;n1<=n;n1++)
    {   
        n2=n1;
        if (n2%k1==0)
        {
            a=a+n1;
            a1=a1+1;
        }
        else 
            b=b+n1;
    }
    b1=n-a1; 
    printf("%.1f  %.1f",a/a1,b/b1); 
    return 0;
}