import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    }
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    }
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    } main {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

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


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      } {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      } if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        } a[i] > b[i] a[i] a i b[i] b i {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } cnt+=b[i] cnt b[i] b i a[i] = a[i] - b[i] a[i] a i a[i] - b[i] a[i] a i b[i] b i b[i] = b[i] - b[i] b[i] b i b[i] - b[i] b[i] b i b[i] b i {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        } if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          } a[i] != 0 a[i] a i 0 {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          } cnt+=a[i] cnt a[i] a i b[i] -= a[i] b[i] b i a[i] a i a[i] -= a[i] a[i] a i a[i] a i if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        } b[i] != 0 b[i] b i 0 {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        } if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          } a[i+1] > b[i] a[i+1] a i+1 i 1 b[i] b i {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } cnt+=b[i] cnt b[i] b i a[i+1] -= b[i] a[i+1] a i+1 i 1 b[i] b i b[i] -= b[i] b[i] b i b[i] b i {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          } if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            } a[i+1]!=0 a[i+1] a i+1 i 1 0 {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            } cnt+=a[i+1] cnt 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] -= a[i+1] a[i+1] a i+1 i 1 a[i+1] a i+1 i 1 System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    }
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    }
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();

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

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

      
      long cnt = 0;
      for(int i = 0; i < n; i++) {
        if(a[i] > b[i]) {
          
          cnt+=b[i];
          a[i] = a[i] - b[i];
          b[i] = b[i] - b[i];


        } else {
          if(a[i] != 0) {
            cnt+=a[i];
            b[i] -= a[i];
            a[i] -= a[i];
          }
        }
        
    
        if(b[i] != 0) {
          if(a[i+1] > b[i]) {
            cnt+=b[i];
            a[i+1] -= b[i];
            b[i] -= b[i];
          } else {
            if(a[i+1]!=0) {
              cnt+=a[i+1];
              b[i] -= a[i+1];
              a[i+1] -= a[i+1];
            }
          }
        }

       
      }

      System.out.println(cnt);
    }
}