
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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	}
} 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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	}
} 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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	} main {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		int[] A = new int[n + 1];
		int[] B = new int[n];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	} 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 int[] C; C long count2 = 0; count2 0 for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n + 1 i n + 1 n 1 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 < n; i++) {
			B[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			B[i] = sc.nextInt();
		} {
			B[i] = sc.nextInt();
		} B[i] = sc.nextInt() B[i] B i sc.nextInt() sc.nextInt sc C = A.clone() C A.clone() A.clone A for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		} int i = n - 1; int i = n - 1; i n - 1 n 1 i >= 0 i 0 i-- i-- i {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		} {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		} if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			} A[i + 1] < B[i] A[i + 1] A i + 1 i 1 B[i] B i {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} count2 += A[i + 1] count2 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 (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			} A[i + 1] == B[i] A[i + 1] A i + 1 i 1 B[i] B i {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} count2 += B[i] count2 B[i] B i A[i + 1] = 0 A[i + 1] A i + 1 i 1 0 B[i] = 0 B[i] B i 0 {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			} count2 += B[i] count2 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 if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			} A[i] < B[i] A[i] A i B[i] B i {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} count2 += A[i] count2 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 (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			} A[i] == B[i] A[i] A i B[i] B i {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} count2 += A[i] count2 A[i] A i A[i] = 0 A[i] A i 0 B[i] = 0 B[i] B i 0 {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			} count2 += B[i] count2 B[i] B i A[i] -= B[i] A[i] A i B[i] B i B[i] = 0 B[i] B i 0 System.out.println(count2) System.out.println System.out System System.out count2 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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	}
} 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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	}
} 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];
		int[] C;
		long count2 = 0;

		for (int i = 0; i < n + 1; i++) {
			A[i] = sc.nextInt();
		}
		for (int i = 0; i < n; i++) {
			B[i] = sc.nextInt();
		}

		C = A.clone();

		for (int i = n - 1; i >= 0; i--) {
			if (A[i + 1] < B[i]) {
				count2 += A[i + 1];
				B[i] -= A[i + 1];
				A[i + 1] = 0;
			} else if (A[i + 1] == B[i]) {
				count2 += B[i];
				A[i + 1] = 0;
				B[i] = 0;

			} else {
				count2 += B[i];
				A[i + 1] -= B[i];
				B[i] = 0;
			}

			if (A[i] < B[i]) {
				count2 += A[i];
				B[i] -= A[i];
				A[i] = 0;
			} else if (A[i] == B[i]) {
				count2 += A[i];
				A[i] = 0;
				B[i] = 0;
			} else {
				count2 += B[i];
				A[i] -= B[i];
				B[i] = 0;
			}
		}

		System.out.println(count2);

	}
}
