#include<bits/stdc++.h>
#define M 200004
using namespace std;

int n, a[M], dp[M];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);     cout.tie(0);

    cin >> n;
    for(int i = 1; i < n; i++)
        cin >> a[i];
    dp[1] = a[1];
    dp[2] = a[1] + a[2];
    for(int i = 3; i < n; i++)
        dp[i] = min(dp[i - 1], dp[i - 2]) + a[i];
    cout << dp[n - 1];
}