#include <iostream>
#include <vector>
using namespace std;

int compute(vector<int> &cost) {
	int n = cost.size();
	vector<int> dp(n + 1, 0);
	dp[1] = cost[0];
	for (int i = 2; i <= n; i++) {
		dp[i] = min(dp[i - 1], dp[i - 2]) + cost[i - 1];
	}
	return min(dp[n], dp[n - 1]);
}

int main() {
	int n;
	cin >> n;
	vector<int> cost(n);
	for (int i = 0; i < n; i++) {
		cin >> cost[i];
	}
	cout << compute(cost) << endl;
	return 0;
}