#include <bits/stdc++.h>

using namespace std;

int n;
vector<int> price;
vector<int> lowestPrice; // lowest price to get to any island

int main()
{
    cin.tie(0);ios::sync_with_stdio(0);
    cin >> n;
    price.resize(n+1);
    lowestPrice.resize(n+1,INT_MAX);

    for(int i = 0; i < n; i++)
    {
        cin >> price[i+1];
    }
    lowestPrice[1] = price[1];
    lowestPrice[2] = price[1]+price[2];
    for(int i = 3; i < n+1;i++)
    {
        lowestPrice[i] = min(lowestPrice[i-1],lowestPrice[i-2])+price[i];
    }

//    bejar(1,price[1]);
    cout << lowestPrice[n];
}