#include <bits/stdc++.h>
#define int long long
using namespace std;
void solve() {
int n;
cin >> n;
vector <int> a(n), b(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
for (int i = 0; i < n; i++) {
cin >> b[i];
}
for (int i = 0; i < n; i++) {
a.push_back(a[i]);
b.push_back(b[i]);
}
int l = 0, r = 1e18;
while (l<r) {
int mid = (l+r)/2;
int cop = mid;
bool pos = true;
for (int i = 2*n-1; i>=n; i--) {
cop-=b[i];
if (cop<a[i]) {
pos = false;
break;
}
}
if (pos) {
r=mid;
} else {
l=mid+1;
}
}
//cout << l << endl;
int cop = l;
for (int i = 2*n-1; i>=n; i--) {
cop-=b[i];
}
int hardest = n;
vector <int> suf(n+1);
for (int i = n-1; i >= 0; i--) {
suf[i]=suf[i+1]+b[i];
}
int small = 1e18;
for (int i = n-1; i >= 0; i--) {
int one = cop-suf[i];
int two = a[hardest]-(suf[i]-suf[hardest]);
if (a[i]>two) {
two = a[i];
hardest=i;
}
int ansi = max(one, two);
small = min(ansi, small);
}
cout << small << endl;
return;
}
signed main() {
int t = 1;
while (t--) {
solve();
}
}
