#include <iostream>
#include <bits/stdc++.h>
using ll = long long;
using namespace std;

const ll INF = 1e18;

int main()
{
    int n; cin >> n;
    vector<ll> a(n);
    vector<ll> b(n);
    ll sumb = 0;
    for (int i = 0; i < n; i++){
        cin >> a[i];
    }
    for (int i = 0; i < n; i++){
        cin >> b[i];
        sumb += b[i];
    }
    ll curans = 0;
    ll minans = 0;
    for (int i = 0; i <= n; i++){
        ll dif = a[i] - b[i];
        curans += dif;
        if (curans > 0){
            curans = 0;
        }
        minans = min(minans, curans);
    }
    cout << sumb + minans;
    return 0;
}