import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] a = new int[n + 1]; a new int[n + 1] n + 1 n 1 int[] b = new int[n]; b new int[n] n for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 i < a.length i a.length a a.length i++ i++ i {
            a[i] = sc.nextInt();
        } {
            a[i] = sc.nextInt();
        } a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 i < b.length i b.length b b.length i++ i++ i {
            b[i] = sc.nextInt();
        } {
            b[i] = sc.nextInt();
        } b[i] = sc.nextInt() b[i] b i sc.nextInt() sc.nextInt sc long hunteredNumber = 0; hunteredNumber 0 for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        } int i = 0; int i = 0; i 0 i < b.length i b.length b b.length i++ i++ i {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        } {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        } long left = Math.min(a[i], b[i]); left Math.min(a[i], b[i]) Math.min Math a[i] a i b[i] b i long right = Math.min(a[i + 1], b[i] - left); right Math.min(a[i + 1], b[i] - left) Math.min Math a[i + 1] a i + 1 i 1 b[i] - left b[i] b i left a[i + 1] -= right a[i + 1] a i + 1 i 1 right hunteredNumber += left + right hunteredNumber left + right left right System.out.println(hunteredNumber) System.out.println System.out System System.out hunteredNumber sc.close() sc.close sc String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    }
} Main
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n + 1];
        int[] b = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        for (int i = 0; i < b.length; i++) {
            b[i] = sc.nextInt();
        }
        long hunteredNumber = 0;
        for (int i = 0; i < b.length; i++) {
            long left = Math.min(a[i], b[i]);
            long right = Math.min(a[i + 1], b[i] - left);
            a[i + 1] -= right;
            hunteredNumber += left + right;
        }
        System.out.println(hunteredNumber);
        sc.close();
    }
}