/*
Telebe of Adicto && Mamedov yani AzeTurk810
I see humans but no humanity
*/
#include <algorithm>
#include <cassert>
#include <iostream>
#include <stack>
#include <vector>
// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
using ll = long long;
using namespace std;
#define ln '\n'
#define INFi 1e9
#define INFll 1e18
#ifdef ONPC
#include <algo.hpp>
#else
#define dbg(...)
#define dbg_out(...)
#define myassert(Expr, Msg) ;
#endif
template <typename T>
struct segtree {
#define lv (v << 1)
#define rv ((v << 1) | 1)
vector<T> sum, lazy, *X;
size_t N;
segtree(int _n, vector<T> &Y) : N(_n), sum(N << 2, 0), lazy(N << 2, 0), X(Y) {
;
};
private:
inline void push(int v, int l, int r) {
if (lazy[v] == 0)
return;
sum[v] -= lazy[v];
myassert(sum[v] >= 0, "WA: sum always must be greater than 0");
if (sum[lv] - lazy[lv] <= lazy[v]) {
lazy[lv] += lazy[v];
} else {
T rs = lazy[v] - sum[lv] + lazy[lv];
lazy[lv] = sum[lv];
lazy[rv] += rs;
}
}
void build(int v, int l, int r) {
if (l == r) {
sum[v] = X[v];
return;
}
int mid = (l + r) >> 1;
build(lv, l, mid);
build(rv, mid + 1, r);
sum[v] = sum[lv] + sum[rv];
}
void upd(int v, int l, int r, int ql, int qr, T val) {
push(v, l, r);
if (ql <= l && r <= qr) {
lazy[v] += val;
push(v, l, r);
return;
}
if (ql > r || qr < l) {
return;
}
int mid = (l + r) >> 1;
push(lv, l, mid);
T vall = min(sum[lv], val);
T valr = val - valr;
upd(lv, l, mid, ql, qr, vall);
upd(rv, mid + 1, r, ql, qr, valr);
sum[v] = sum[lv] + sum[rv];
}
T ask(int v, int l, int r, int ql, int qr, T val) {
;
}
};
inline void systemd() {
}
char solve() {
size_t n;
if (!(cin >> n))
return 1;
vector<int> X(n), Y(n);
for (int &x : X)
cin >> x;
for (int &y : Y)
cin >> y;
stack<size_t> st;
ll ans = 0;
for (size_t i = 0; i < n; i++) {
while (!st.empty() && Y[i] > 0) {
size_t j = st.top();
st.pop();
ll x = min(X[j], Y[i]);
X[j] -= x;
Y[i] -= x;
ans += x;
if (X[j] > 0)
st.push(j);
}
if (X[i] > 0)
st.push(i);
}
for (size_t i = 0; i < n; i++) {
Y[i] -= X[i];
}
for (size_t i = 0; i < n; i++) {
if (Y[i] > 0) {
ans -= Y[i];
}
}
cout << ans << ln;
systemd();
return 0;
}
// Attack on titan<3
signed main() {
ios::sync_with_stdio(0);
cin.tie(nullptr);
int t = 1e9;
// cin >> t;
for (int cases = 0; cases < t; cases++) {
if (solve())
break;
#ifdef ONPC
cerr << "__________\n";
#endif
}
}
// Just Imaginary
/*
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣀⣀⠀⠀⠀⢀⣴⣾⠀⠀⠀⡀⢀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣦⣾⣿⣿⣿⣿⣿⡆⠁⠀⢀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠹⣿⣿⣿⣿⣿⣿⣿⣿⡿⠁⠀⡠⠂⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠠⠔⠚⣿⣿⣿⣿⣿⣦⡄⠀⠁⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⢀⠠⠐⢂⠉⡀⣀⣤⣄⢻⣿⣿⡟⢈⡹⣿⡀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⡀⠄⠂⠈⠀⣶⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠘⣷⡀⠀⡀⠐⠂⠐⢄
⠀⠀⠀⠀⠀⠀⠀⣿⣿⠟⠿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⣀⣾⣷⠯⠀⠤⠤⠄⠈
⠀⠀⠀⠀⠀⠀⣼⣿⡟⠀⠀⣹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⡀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⣰⣿⠋⠀⠀⢠⣾⣿⣿⣿⣿⣿⣭⠟⢻⣿⣿⣿⣿⡿⠁⠀⠀⠀⠀
⠀⠀⠀⣀⣶⡟⠁⠀⢾⣶⣿⠟⠉⠈⢻⣿⣿⣿⣦⣜⠀⠛⠛⠿⠁⠀⠀⠀⠀⠀
⠚⠻⠿⠿⡿⠁⠀⢠⣿⣿⠁⠀⣠⠖⠋⠉⠻⣿⣿⣿⣶⡀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⣰⣿⡿⠃⠠⠊⠁⠀⠀⠀⠀⠈⢿⣿⣿⠟⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⢀⣴⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⣠⣾⠏⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⢀⣴⠾⠟⠛⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
*/
