#include <bits/stdc++.h>

using namespace std;

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

void bejar(int s,int cost)
{
    if(s == n-1)
    {
        if(lowestPrice[s+1] > cost+ price[s+1])
        {
            lowestPrice[s+1] = cost+ price[s+1];
            bejar(s+1,lowestPrice[s+1]);
        }
    }
    else if(s != n)
    {
        if(lowestPrice[s+1] > cost+ price[s+1])
        {
            lowestPrice[s+1] = cost+ price[s+1];
            bejar(s+1,lowestPrice[s+1]);
        }
        if(lowestPrice[s+2] > cost+ price[s+2])
        {
            lowestPrice[s+2] = cost+ price[s+2];
            bejar(s+2,lowestPrice[s+2]);
        }
    }

}
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];
    }

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