为什么wa 了

#include <bits/stdc++.h>
using namespace std;
int n,m;
int hrt[3010];
int ans;
int sum;
int main()
{
    cin>>n>>m;
    for(int i=0;i<=n;i++) 
        scanf("%d",&hrt[i]),ans=i<=m?sum+=hrt[i]:min(ans,sum+=hrt[i]-hrt[i-m]);
    cout<<ans;
    return 0;
}