#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define pll pair<long, long>
#define endl "\n"
#define first fs
#define second sc
#define vll vector<ll>

void solve()
{
	ll n;
	cin >> n;
	vll a(n);
	for(ll i = 0; i < n; i++) 
		cin >> a[i];
	vll dp(n);
	dp[0] = a[0];
	dp[1] = a[0]+a[1];
	for(ll i = 2; i < n; i++)
		dp[i] = min(dp[i-1]+a[i], dp[i-2]+a[i]);
	cout << dp[n-1] << endl;
}

int main() 
{
	cin.tie(NULL); cout.tie(NULL);
	ios_base::sync_with_stdio(false);
	ll t = 1;
	//cin >> t;
	while(t--) solve();
	return 0;
}