import java.util.Scanner;
import java.util.Arrays;

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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	}
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays 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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	}
} 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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



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

		int n=sc.nextInt();
		int a[]=new int [n+1];
		int b[]=new int[n];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	} 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 long count=0; count 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 for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		} int i=n; int i=n; i n i>=1 i 1 i-- i-- i {
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		} {
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		} if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			} a[i]>=b[i-1] a[i] a i b[i-1] b i-1 i 1 {
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			} count+=b[i-1] count b[i-1] b i-1 i 1 a[i]-=b[i-1] a[i] a i b[i-1] b i-1 i 1 b[i-1]=0 b[i-1] b i-1 i 1 0 {
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			} count+=a[i] count a[i] a i b[i-1]-=a[i] b[i-1] b i-1 i 1 a[i] a i a[i]=0 a[i] a i 0 if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			} a[i-1]>=b[i-1] a[i-1] a i-1 i 1 b[i-1] b i-1 i 1 {
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			} count+=b[i-1] count b[i-1] b i-1 i 1 a[i-1]-=b[i-1] a[i-1] a i-1 i 1 b[i-1] b i-1 i 1 b[i-1]=0 b[i-1] b i-1 i 1 0 {
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			} count+=a[i-1] count a[i-1] a i-1 i 1 b[i-1]-=a[i-1] b[i-1] b i-1 i 1 a[i-1] a i-1 i 1 a[i-1]=0 a[i-1] a i-1 i 1 0 System.out.println(count) System.out.println System.out System System.out count 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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	}
} 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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	}
} Main
import java.util.Scanner;
import java.util.Arrays;

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];

		long count=0;

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

		for(int i=n;i>=1;i--){
			if(a[i]>=b[i-1]){
				count+=b[i-1];
				a[i]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i];
				b[i-1]-=a[i];
				a[i]=0;
			}
			if(a[i-1]>=b[i-1]){
				count+=b[i-1];
				a[i-1]-=b[i-1];
				b[i-1]=0;
			}else{
				count+=a[i-1];
				b[i-1]-=a[i-1];
				a[i-1]=0;
			}
		}

		System.out.println(count);



	}
}
