import java.util.*;
import java.io.*;

public class Main
{
	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;i++)
		{
			a[i]=in.nextInt();

		}
		for(int i=0;i<n;i++)
		{			
			b[i]=in.nextInt();
		}
		long ans=0;
		if(a[n]>b[n-1])
		{
			ans=b[n-1];
			b[n-1]=0;
		}
		else
		{
			ans=a[n];
			b[n-1]=b[n-1]-a[n];
		}
		for(int i=n-1;i>0;i--)
		{
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		}
		if(a[0]>b[0])
		{
			ans=ans+b[0];
		}
		else
		{
			ans+=a[0];
		}
		System.out.println(ans);
			
	}
}
	 import java.util.*; util.* java import java.io.*; io.* java public class Main
{
	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;i++)
		{
			a[i]=in.nextInt();

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

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

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

		} int i=0; int i=0; i 0 i<=n i n i++ i++ i {
			a[i]=in.nextInt();

		} {
			a[i]=in.nextInt();

		} a[i]=in.nextInt() a[i] a i in.nextInt() in.nextInt in for(int i=0;i<n;i++)
		{			
			b[i]=in.nextInt();
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {			
			b[i]=in.nextInt();
		} {			
			b[i]=in.nextInt();
		} b[i]=in.nextInt() b[i] b i in.nextInt() in.nextInt in long ans=0; ans 0 if(a[n]>b[n-1])
		{
			ans=b[n-1];
			b[n-1]=0;
		}
		else
		{
			ans=a[n];
			b[n-1]=b[n-1]-a[n];
		} a[n]>b[n-1] a[n] a n b[n-1] b n-1 n 1 {
			ans=b[n-1];
			b[n-1]=0;
		} ans=b[n-1] ans b[n-1] b n-1 n 1 b[n-1]=0 b[n-1] b n-1 n 1 0 {
			ans=a[n];
			b[n-1]=b[n-1]-a[n];
		} ans=a[n] ans a[n] a n b[n-1]=b[n-1]-a[n] b[n-1] b n-1 n 1 b[n-1]-a[n] b[n-1] b n-1 n 1 a[n] a n for(int i=n-1;i>0;i--)
		{
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		} int i=n-1; int i=n-1; i n-1 n 1 i>0 i 0 i-- i-- i {
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		} {
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		} if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			} a[i]-b[i]>0 a[i]-b[i] a[i] a i b[i] b i 0 {
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			} if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				} a[i]-b[i-1]-b[i]>0 a[i]-b[i-1]-b[i] a[i]-b[i-1]-b[i] a[i] a i b[i-1] b i-1 i 1 b[i] b i 0 {
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				} ans=ans+b[i]+b[i-1] ans ans+b[i]+b[i-1] ans+b[i]+b[i-1] ans b[i] b i b[i-1] b i-1 i 1 b[i-1]=0 b[i-1] b i-1 i 1 0 {
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				} ans=ans+a[i] ans ans+a[i] ans a[i] a i b[i-1]=b[i-1]+b[i]-a[i] b[i-1] b i-1 i 1 b[i-1]+b[i]-a[i] b[i-1]+b[i] b[i-1] b i-1 i 1 b[i] b i a[i] a i {
				ans=ans+a[i];
			} ans=ans+a[i] ans ans+a[i] ans a[i] a i if(a[0]>b[0])
		{
			ans=ans+b[0];
		}
		else
		{
			ans+=a[0];
		} a[0]>b[0] a[0] a 0 b[0] b 0 {
			ans=ans+b[0];
		} ans=ans+b[0] ans ans+b[0] ans b[0] b 0 {
			ans+=a[0];
		} ans+=a[0] ans a[0] a 0 System.out.println(ans) System.out.println System.out System System.out ans String [] Args Args public class Main
{
	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;i++)
		{
			a[i]=in.nextInt();

		}
		for(int i=0;i<n;i++)
		{			
			b[i]=in.nextInt();
		}
		long ans=0;
		if(a[n]>b[n-1])
		{
			ans=b[n-1];
			b[n-1]=0;
		}
		else
		{
			ans=a[n];
			b[n-1]=b[n-1]-a[n];
		}
		for(int i=n-1;i>0;i--)
		{
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		}
		if(a[0]>b[0])
		{
			ans=ans+b[0];
		}
		else
		{
			ans+=a[0];
		}
		System.out.println(ans);
			
	}
} public class Main
{
	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;i++)
		{
			a[i]=in.nextInt();

		}
		for(int i=0;i<n;i++)
		{			
			b[i]=in.nextInt();
		}
		long ans=0;
		if(a[n]>b[n-1])
		{
			ans=b[n-1];
			b[n-1]=0;
		}
		else
		{
			ans=a[n];
			b[n-1]=b[n-1]-a[n];
		}
		for(int i=n-1;i>0;i--)
		{
			if(a[i]-b[i]>0)
			{
				if(a[i]-b[i-1]-b[i]>0)
				{
					ans=ans+b[i]+b[i-1];
					b[i-1]=0;
				}
				else
				{
					ans=ans+a[i];
					b[i-1]=b[i-1]+b[i]-a[i];
				}
			}
			else
			{
				ans=ans+a[i];
			}
		}
		if(a[0]>b[0])
		{
			ans=ans+b[0];
		}
		else
		{
			ans+=a[0];
		}
		System.out.println(ans);
			
	}
} Main
import java.util.*;
import java.io.*;

public class Main
{
	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;i++)
		{
			a[i]=in.nextInt();

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