#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
const ll LOG = 31;
const ll MOD = 1000000007;
const ll inf = 1e17;
const ll B = 2305843009213693951;
#define db(x) cerr << #x << " = " << x << " | "
#define dbg(x) cerr << #x << " = " << x << "\n"
#define Algerian ios::sync_with_stdio(0);
#define OI cin.tie(NULL);
int main() {
Algerian OI
ll n;
cin >> n;
vector<ll> x(n), y(n);
for (ll& c : x) cin >> c;
for (ll& c : y) cin >> c;
deque<ll> dq;
for (ll i = 0; i < n; i++) dq.push_back(i);
ll res = 0;
for (ll i = 0; i < n; i++) {
while (y[i]) {
ll c = dq.front();
ll s = min(y[i], x[c]);
y[i] -= s;
x[c] -= s;
if (x[c] == 0) dq.pop_front();
ll sign = (i - c > 0) - (i - c < 0);
res += sign * s;
}
}
cout << res << "\n";
return 0;
}
