// nt22-23 szigetek.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <deque>
#include <algorithm>

using namespace std;

deque<pair<int, int>>x;
int i, j, n;

int main()
{
    cin >> n;
    x.resize(n + 1);
    for (i = 1; i <= n; ++i) cin >> x[i].first;
    x[1].second = x[1].first;
    x[2].second = x[1].second + x[2].first;
    for (i = 3; i <= n; ++i)
    {
        x[i].second = min(x[i - 1].second, x[i - 2].second) + x[i].first;
    }
    cout << x[n].second;
    return 0;
}
/*
6
3 5 9 7 1 6
*/
// 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