// UUID: 6d5f78c9-2a32-475d-af08-e0d6405a4fb2
#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
	int n; cin >> n;
    vector<int> cost(n);
    for(int i = 0; i < n; ++i) cin >> cost[i];
    if (n == 1){ 
		cout << cost[0]; 
		return 0;
	}

    vector<ll> dp(n);
    dp[0] = cost[0];
    dp[1] = cost[0] + cost[1];

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

    cout << dp[n-1] << endl;
    return 0;
}