// UUID: 585cc8e2-3703-402a-b9d6-933caf57ea73
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    int N;
    cin >> N;

    vector<long long> d(N + 1);
    for (int i = 1; i <= N; i++) {
        cin >> d[i];
    }
    vector<long long> dp(N + 1);

    dp[1] = d[1];
    if (N >= 2)
        dp[2] = d[1] + d[2];

    for (int i = 3; i <= N; i++) {
        dp[i] = d[i] + min(dp[i - 1], dp[i - 2]);
    }

    cout << dp[N] << endl;
    return 0;
}