#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int n;
    cin >> n;

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

    vector<int> distances(n);
    distances[0] = 0;
    for (int i = 1; i < n; i++) {
        distances[i] = min(i, n - i);
    }

    vector<int> optimal(n);

    optimal[0] = d[0];
    if (n > 1) {
        optimal[1] = min(d[0] + d[1], d[1]);
    }

    for (int i = 2; i < n; i++) {
        optimal[i] = min(optimal[i-1] + d[i], optimal[i-2] + min(d[i-1], d[i]));
    }

    int result = optimal[n-1];

    if (distances[n-1] == 1) {
        result = min(result, d[n-2]);
    }

    cout << result << endl;

    return 0;
}