import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    }

} import java.util.*; util.* java public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    }

} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc long[] a = new long[n+1]; a new long[n+1] n+1 n 1 long[] b = new long[n]; b new long[n] n for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        } int i = 0; int i = 0; i 0 i < n+1 i n+1 n 1 i++ i++ i {
            a[i] = sc.nextLong();
        } {
            a[i] = sc.nextLong();
        } a[i] = sc.nextLong() a[i] a i sc.nextLong() sc.nextLong sc for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            b[i] = sc.nextLong();
        } {
            b[i] = sc.nextLong();
        } b[i] = sc.nextLong() b[i] b i sc.nextLong() sc.nextLong sc long ans = 0l; ans 0l for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        } int i = 0; int i = 0; i 0 i < n/2 +1 i n/2 +1 n/2 n 2 1 i++ i++ i {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        } {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        } if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            } b[i] <= a[i] b[i] b i a[i] a i {
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            } ans += b[i] ans b[i] b i a[i] -= b[i] a[i] a i b[i] b i b[i] = 0 b[i] b i 0 {
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            } ans += a[i] ans a[i] a i b[i] -= a[i] b[i] b i a[i] a i a[i] = 0 a[i] a i 0 if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                } b[i] <= a[i+1] b[i] b i a[i+1] a i+1 i 1 {
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                } ans += b[i] ans b[i] b i a[i+1] -= b[i] a[i+1] a i+1 i 1 b[i] b i b[i] = 0 b[i] b i 0 {
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                } ans += a[i+1] ans a[i+1] a i+1 i 1 b[i] -= a[i+1] b[i] b i a[i+1] a i+1 i 1 a[i+1] = 0 a[i+1] a i+1 i 1 0 if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            } i < n - 1 - i i n - 1 - i n - 1 - i n 1 i {
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            } if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                } b[n - 1 - i] <= a[n - i] b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[n - i] a n - i n i {
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                } ans += b[n - 1 - i] ans b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[i] -= b[n - 1 - i] a[i] a i b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i b[n - 1 - i] = 0 b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i 0 {
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                } ans += a[n - i] ans a[n - i] a n - i n i b[n - 1 - i] -= a[n - i] b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[n - i] a n - i n i a[n-i] = 0 a[n-i] a n-i n i 0 if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    } b[n - 1 - i] <= a[n - i - 1] b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[n - i - 1] a n - i - 1 n - i - 1 n i 1 {
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    } ans += b[n - 1 - i] ans b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[n - i -1] -= b[n - 1 - i] a[n - i -1] a n - i -1 n - i -1 n i 1 b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i b[n - 1 - i] = 0 b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i 0 {
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    } ans += a[n-i-1] ans a[n-i-1] a n-i-1 n-i-1 n i 1 b[n - 1 - i] -= a[n-i-1] b[n - 1 - i] b n - 1 - i n - 1 - i n 1 i a[n-i-1] a n-i-1 n-i-1 n i 1 a[n-i-1] = 0 a[n-i-1] a n-i-1 n-i-1 n i 1 0 System.out.println(ans) System.out.println System.out System System.out ans 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();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    }

} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    }

} Main
import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n+1];
        long[] b = new long[n];
        for (int i = 0; i < n+1; i++) {
            a[i] = sc.nextLong();
        }
        for (int i = 0; i < n; i++) {
            b[i] = sc.nextLong();
        }
        long ans = 0l;
        for (int i = 0; i < n/2 +1; i++) {
            if(b[i] <= a[i]){
                ans += b[i];
                a[i] -= b[i];
                b[i] = 0;
            }else{
                ans += a[i];
                b[i] -= a[i];
                a[i] = 0;
                if(b[i] <= a[i+1]){
                    ans += b[i];
                    a[i+1] -= b[i];
                    b[i] = 0;
                }else{
                    ans += a[i+1];
                    b[i] -= a[i+1];
                    a[i+1] = 0;
                }
            }
            if(i < n - 1 - i){
                if(b[n - 1 - i] <= a[n - i]){
                    ans += b[n - 1 - i];
                    a[i] -= b[n - 1 - i];
                    b[n - 1 - i] = 0;
                }else{
                    ans += a[n - i];
                    b[n - 1 - i] -= a[n - i];
                    a[n-i] = 0;
                    if(b[n - 1 - i] <= a[n - i - 1]){
                        ans += b[n - 1 - i];
                        a[n - i -1] -= b[n - 1 - i];
                        b[n - 1 - i] = 0;
                    }else{
                        ans += a[n-i-1];
                        b[n - 1 - i] -= a[n-i-1];
                        a[n-i-1] = 0;
                    }
                }
            }
        }

        System.out.println(ans);
        sc.close();

    }

}
