import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] arr = new int[n+1]; arr new int[n+1] n+1 n 1 int[] arr1 = new int[n]; arr1 new int[n] n for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    } int i=0; int i=0; i 0 i<n+1 i n+1 n 1 i++ i++ i {
      arr[i]=sc.nextInt();
    } {
      arr[i]=sc.nextInt();
    } arr[i]=sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    } int i=0; int i=0; i 0 i<n i n i++ i++ i {
      arr1[i]=sc.nextInt();
    } {
      arr1[i]=sc.nextInt();
    } arr1[i]=sc.nextInt() arr1[i] arr1 i sc.nextInt() sc.nextInt sc long sum=0; sum 0 for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    } int i=0; int i=0; i 0 i<n i n i++ i++ i {
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    } {
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    } if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      } arr[i]+arr[i+1]<=arr1[i] arr[i]+arr[i+1] arr[i] arr i arr[i+1] arr i+1 i 1 arr1[i] arr1 i {
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      } sum=sum+arr[i]+arr[i+1] sum sum+arr[i]+arr[i+1] sum+arr[i]+arr[i+1] sum arr[i] arr i arr[i+1] arr i+1 i 1 arr[i]=0 arr[i] arr i 0 arr[i+1]=0 arr[i+1] arr i+1 i 1 0 {
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      } if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        } arr[i]<=arr1[i] arr[i] arr i arr1[i] arr1 i {
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        } arr[i+1]=arr[i+1]-(arr1[i]-arr[i]) arr[i+1] arr i+1 i 1 arr[i+1]-(arr1[i]-arr[i]) arr[i+1] arr i+1 i 1 (arr1[i]-arr[i]) arr1[i] arr1 i arr[i] arr i arr[i]=0 arr[i] arr i 0 {
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        } arr[i]=arr[i]-arr1[i] arr[i] arr i arr[i]-arr1[i] arr[i] arr i arr1[i] arr1 i sum=sum+arr1[i] sum sum+arr1[i] sum arr1[i] arr1 i System.out.println(sum) System.out.println System.out System System.out sum String[] args args public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  }
} public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  }
} Main
import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] arr = new int[n+1];
    int[] arr1 = new int[n];
    for(int i=0;i<n+1;i++){
      arr[i]=sc.nextInt();
    }
    for(int i=0;i<n;i++){
      arr1[i]=sc.nextInt();
    }
    long sum=0;
    for(int i=0;i<n;i++){
 
      if(arr[i]+arr[i+1]<=arr1[i]){
     //   System.out.println("verma");
        sum=sum+arr[i]+arr[i+1];
        arr[i]=0;
        arr[i+1]=0;
      }
      else{
       
        if(arr[i]<=arr1[i]){
   //        System.out.println("anuj");
          arr[i+1]=arr[i+1]-(arr1[i]-arr[i]);
          arr[i]=0;
       //   System.out.println(arr[i+1]);
        }
        else{
   //       System.out.println("anuj1");
          arr[i]=arr[i]-arr1[i];
        }
         sum=sum+arr1[i];
      }
    }
    System.out.println(sum);
  }
}