#include <iostream>
using namespace std;
const int N = 100010;
int f[N];
int cost[N];
int main() {
    int n;
    cin >> n;
    for(int i = 1; i <= n; i ++) cin >> cost[i];
    f[1] = cost[1], f[2] = cost[2];
    for(int i = 3; i <= n + 1; i ++){
        f[i] = min(f[i - 1] + cost[i], f[i - 2] + cost[i]);
    }
    cout << f[n + 1] << endl;
    return 0;
}