#include <iostream>

using namespace std;

int n;
int M[20];
int lol(int i){
    if(i >= n) return 0;
    return M[i] + min(lol(i+1), lol(i+2));
}

int main(){
    cin >> n;
    for(int i = 0; i < n; i++){
        cin >> M[i];
    }
    cout << lol(-1) << endl;
    return 0;
}
