#include <bits/stdc++.h>
using namespace std;

#define int long long
#define nn "\n"

const long long INF = 4e18;
const int N = 1505;

int n;
int a[N];
long long dp[N][N];

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for(int i = 1; i <= n - 1; i++){
        cin >> a[i];
    }

    for(int i = 0; i <= n; i++){
        for(int j = 0; j <= n; j++){
            dp[i][j] = INF;
        }
    }

    dp[0][1] = 0;

    long long ans = INF;

    for(int i = 0; i <= n - 1; i++){
        for(int j = 1; j <= n; j++){
            if(dp[i][j] == INF) continue;

            if(i + j >= n){
                ans = min(ans, dp[i][j]);
            }

            for(int k = i + 1; k <= min((long long)n - 1, i + j); k++){

                // vào sưởi
                dp[k][j] = min(dp[k][j], dp[i][j] + 1);

                // mua áo
                dp[k][j + 1] = min(dp[k][j + 1],
                                   dp[i][j] + a[k]);
            }
        }
    }

    cout << ans << nn;
    return 0;
}