#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
template<class Key, class Compare = less<Key>>
using indexed_set = tree<Key, null_type, Compare, rb_tree_tag, tree_order_statistics_node_update>;
template<class Key, class Value, class Compare = less<Key>>
using indexed_map = tree<Key, Value, Compare, rb_tree_tag, tree_order_statistics_node_update>;
template<class Key>
using hash_set = gp_hash_table<
Key, null_type, hash<Key>, equal_to<Key>, direct_mask_range_hashing<Key>, linear_probe_fn<>,
hash_standard_resize_policy<hash_exponential_size_policy<>, hash_load_check_resize_trigger<true>, true>>;
template<class Key, class Value>
using hash_map = gp_hash_table<
Key, Value, hash<Key>, equal_to<Key>, direct_mask_range_hashing<Key>, linear_probe_fn<>,
hash_standard_resize_policy<hash_exponential_size_policy<>, hash_load_check_resize_trigger<true>, true>>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// https://codeforces.com/blog/entry/79148
class Timer: chrono::high_resolution_clock {
const time_point start_time;
public:
Timer(): start_time(now()) {}
rep elapsed_time() const {
return chrono::duration_cast<chrono::milliseconds>(now() - start_time).count();
}
} timer;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, pf = 0, l = 0, r = 0;
cin >> n;
vector<int> x(n), y(n);
for (int i = 0; i < n; i++) {
cin >> x[i];
}
for (int i = 0; i < n; i++) {
cin >> y[i];
pf += x[i];
l += max(0, y[i] - pf);
pf -= min(y[i], pf);
r += y[i];
}
auto test = [&] (int k) {
int p = 0, res1 = 0, res2 = 0, k_ori = k;
vector<int> x2 = x;
for (int i = 0; i < n; i++) {
int cur = y[i] - min(k, y[i]);
k -= min(k, y[i]);
while (cur) {
int d = min(cur, x2[p]);
cur -= d;
x2[p] -= d;
if (p < i) {
res1 += d;
}
if (!x2[p]) {
p++;
}
}
}
k = k_ori + 1;
x2 = x;
p = 0;
for (int i = 0; i < n; i++) {
int cur = y[i] - min(k, y[i]);
k -= min(k, y[i]);
while (cur) {
int d = min(cur, x2[p]);
cur -= d;
x2[p] -= d;
if (p < i) {
res2 += d;
}
if (!x2[p]) {
p++;
}
}
}
return make_pair(res1, res2);
};
if (l == r) {
cout << test(l).first - l;
return 0;
}
r--;
while (r - l > 2) {
int m = (l + r) / 2;
pair<int, int> res = test(m);
if (res.second - res.first > 0) {
l = m;
}
else {
r = m;
}
}
if (test(l).second - test(l).first <= 0) {
cout << test(l).first - l;
}
else if (test(l + 1).second - test(l + 1).first <= 0) {
cout << test(l + 1).first - l - 1;
}
else {
cout << test(r).first - r;
}
return 0;
}
