前缀和

#include<bits/stdc++.h>
using namespace std;
int pre[10005],a[10005];
bool cmp(int a,int b){return a > b;}
int main(){
    int n,k; cin >> n >> k;
    for(int i = 1;i <= n;i++){
        cin >> a[i];
        pre[i] = pre[i - 1] + a[i];
    }
    int ans = 0;
    for(int i = k + 1;i <= n;i++){
        int t = pre[i] - pre[i - k - 1];
        ans = max(ans,t);
    }
    cout << ans;
    return 0;
}