#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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