再遇四渠注水问题！

import java.util.Scanner;

public class C {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int a[] = new int[n + 1];
        int b[] = new int[n];
        for (int i = 0; i < n + 1; i++) {
            a[i] = in.nextInt();
        }
        for (int i = 0; i < n; i++) {
            b[i] = in.nextInt();
        }
        long ans = 0;
        for (int i = 0; i < n; i++) {
            if (b[i] >= a[i]) {
                ans += a[i];
                b[i] -= a[i];
            } else {
                ans += b[i];
                b[i] = 0;
            }
            if (b[i] >= a[i + 1]) {
                ans += a[i + 1];
                b[i] -= a[i + 1];
                a[i + 1] = 0;
            } else {
                ans += b[i];
                a[i + 1] -= b[i];
                b[i] = 0;
            }
        }
        System.out.println(ans);
        in.close();
    }
}