#include <bits/stdc++.h>
 
#define ll long long
 
using namespace std;
 
const int MAXN = 1e6 + 11;
int n;
ll a[MAXN], b[MAXN], dp[MAXN];
 
int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	//freopen("THAMQUAN.INP", "r", stdin);
	//freopen("THAMQUAN.OUT", "w", stdout);
	cin >> n;
 
	for(int i = 1; i <= n; ++i) cin >> a[i];
	for(int i = 1; i <= n - 2; ++i) cin >> b[i];
 
	dp[1] = a[1];
	dp[2] = a[1] + a[2];
	for(int i = 3; i <= n; ++i) {
		dp[i] = min(dp[i - 1] + a[i], dp[i - 2] + b[i - 2] + a[i]);
	}
 
 
 
	cout << dp[n];
 
	return 0;
}

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