#include <bits/stdc++.h>

using namespace std;

const int INF = 2e9 + 7;

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

    vector<int> arak(n);

    for(int i = 0; i < n; i++){
        cin >> arak[i];
    }

    vector<int> dp(n, INF);
    dp[0] = arak[0];
    for(int i = 0; i < n; i++){
        if(i + 1 < n){
            dp[i + 1] = min(dp[i] + arak[i + 1], dp[i + 1]);
        }

        if(i + 2 < n){
            dp[i + 2] = min(dp[i] + arak[i + 2], dp[i + 2]);
        }
    }

    cout << dp[n - 1] << "\n";
}