#include<bits/stdc++.h>
using namespace std;
 
#define ll long long
 
void solve(){
    int n,k,s=0,mx=INT_MIN;
    cin>>n;
    vector<int>v(n);
    for(int i=0;i<n;i++)cin>>v[i];
    cin>>k;
    for(int i=0;i<k;i++){
        s+=v[i];
    }
    mx=max(mx,s);
    int a=k;
    for(int i=n-1;i>=n-a;i--){
        s+=v[i];
        s-=v[k-1];
        k--;
        mx=max(mx,s);
    }
    cout<<mx<<"\n";
}
 
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
    return 0;
}

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5
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3