// Szigetk.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin >> n;
    vector<long long> dp(n+1);
    dp[0] = 0;
    cin >> dp[1];
    
    for (int i = 2; i <= n; i++)
    {
        
        int x;
        cin >> x;
        if (i == 2)
            dp[i] = dp[1] + x;
        else
        dp[i] = x+min(dp[i - 1], dp[i - 2]);
    }
    cout << dp[n];
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started: 
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file