#include <iostream>
#include <vector>

using namespace std;


int main()
{
    int n;
    cin >> n;
    vector <int> v(n);
    vector <int> dp(n);
    vector <bool> sin(n);

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

    dp[0] = v[0];
    dp[1] = v[0] + v[1];

    for(int i = 2; i < n; i++)
    {
        dp[i] = min(dp[i - 1], dp[i - 2]) + v[i];
    }
    cout <<  dp[n - 1];
}