/*
Decelerating Jump
https://qoj.ac/problem/2283

DP

*/

#include <cstdio>
#include <iostream>

using namespace std;

int sqr[3005];
long long mem[3005][3005];

long long solve(int i, int maxi, int n){
  //printf("Proc %d, %d\n", i, maxi);
  long long ans = -1e15, aux;
  int k;

  if(mem[i][maxi] != -1e15)
    ans = mem[i][maxi];
  else{
    if(i == n - 1)
      ans = sqr[i];
    else{
      //printf("Aca %d, %d\n");
      for(k = i + 1; k <= min(n - 1, i + maxi); ++k){
	aux = solve(k, k - i, n);
	if(aux != -1e15){
	  ans = max(ans, aux + sqr[i]);
	  //printf("Mejor ahora %d, %d es %lli\n", i, maxi, ans);
	}
      }
    }

    mem[i][maxi] = ans;

    //printf("Res %d, %d, %lli\n", i, maxi, ans);
  }
   
  return ans;
}

int main(){
  int i, j, n;
  long long ans;
  scanf("%d", &n);
  for(i = 0; i < n; ++i)
    scanf("%d", sqr + i);
  for(i = 0; i < n + 1; ++i)
    for(j = 0; j < n + 1; ++j)
      mem[i][j] = -1e15;
  ans = solve(0, n - 1, n);
  printf("%lli\n", ans);
  return 0;
}