#include<iostream>
#include<vector>
using namespace std;
int n;
int main(){
cin >> n;
vector<int> a(n + 5,0),dp(n + 5,0);
for(int i = 1;i <= n;i++) cin >> a[i];
for(int i = 1;i <= n;i++){
for(int j = i;j <= n;j++){
dp[j] = max(dp[j],dp[j - i] + a[i]);
}
}
cout << dp[n];
return 0;
}
