#include <bits/stdc++.h>
using namespace std;
int a[41],n,dp[50];
int main(){
	scanf("%d",&n);
	for(int i = 1;i<=n;i++)scanf("%d",&a[i]);
	for(int i = 1;i<=n;i++)dp[i] = min(dp[i-1]+a[i],dp[i-2]+a[i]);
	printf("%d",min(dp[n],dp[n-1]));
	return 0;
}