Problem:
Score : 300 points

Problem Statement

There are N+1 towns. The i-th town is being attacked by A_i monsters.

We have N heroes. The i-th hero can defeat monsters attacking the i-th or (i+1)-th town, for a total of at most B_i monsters.

What is the maximum total number of monsters the heroes can cooperate to defeat?

Constraints

All values in input are integers.

1 \leq N \leq 10^5

1 \leq A_i \leq 10^9

1 \leq B_i \leq 10^9

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_{N+1}
B_1 B_2 ... B_N

Output

Print the maximum total number of monsters the heroes can defeat.

Sample Input 1

2
3 5 2
4 5

Sample Output 1

9

If the heroes choose the monsters to defeat as follows, they can defeat nine monsters in total, which is the maximum result.

The first hero defeats two monsters attacking the first town and two monsters attacking the second town.

The second hero defeats three monsters attacking the second town and two monsters attacking the third town.

Sample Input 2

3
5 6 3 8
5 100 8

Sample Output 2

22

Sample Input 3

2
100 1 1
1 100

Sample Output 3

3

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)


// Java program For handling Input/Output 
import java.io.*; 
import java.util.*;
import java.math.*;


public class Main 
{ 
    Scanner sc;

//actual logic
void solve(){
    int n = ni();
    int a[] = new int[n+1];
    int b[] = new int[n];

    ia(a);
    ia(b);

    int ans = 0;

    int i = 0;
    while(i < n)
    {
        if(b[i] >= a[i])
        {
            ans += a[i];
            int sec = b[i] - a[i];
            a[i] = 0;
            if(sec > 0)
            {
                if(sec >= a[i+1])
                {
                    ans += a[i+1];
                    a[i+1] = 0;
                }
                else
                {
                    ans += sec;
                    a[i+1] -= sec;
                }
            }
        }
        else
        {
            ans += b[i];
            a[i] -= b[i];
        }
        i++;
    }
    /*for(i = 0;i < n+1;i++)
        System.out.print(a[i] + " ");
        */
    System.out.println(ans);
}


//constructor
    Main(){
        try{  
            sc = new Scanner(System.in);
        }catch(Exception e){
            System.out.println(e);
        }
    }


//main metohd
    public static void main(String[] args) 
    { 
    	new Main().solve();
    }


//Utility methods
    //input an integer from scanner
    int ni()
    {
        int a = sc.nextInt();
        return a;
    }
    //input a long from scanner
    long nl()
    {
        return sc.nextLong();
    }
    //input a float from scanner
    float nf(){
        float a = sc.nextFloat();
        return a;
    }
    //input a double from scanner
    double nd(){
        double a = sc.nextDouble();
        return a;
    }
    //input a sentence from scanner
    String ns(){
        return sc.nextLine();
    }
    //converts a string to stringtokenizer
    StringTokenizer nst(String s){
        return new StringTokenizer(s);
    }
    //input an intger array
    void ia(int a[]){
        for(int i = 0;i < a.length;i++)
            a[i] = sc.nextInt();
    }
    //
    void la(long a[]){
        for(int i = 0;i < a.length;i++)
            a[i] = sc.nextLong();
    }
    //input a float array
    void fa(float a[]){
        for(int i = 0;i < a.length;i++)
            a[i] = sc.nextFloat();
    }
    //input a double array
    void da(double a[]){
        for(int i = 0;i < a.length;i++)
            a[i] = sc.nextDouble();
    }
    //input a string array either with all empty input or from scanner
    void sa(String a[], boolean empty){
        if(empty)
        {
            for(int i = 0;i < a.length;i++)
            {
                a[i] = "";
            }
        }
        else
        {
            for(int i = 0;i < a.length;i++)
            {
                a[i] = ns();
            }
        }
    }
    //input two dimensional integer array
    void ida(int a[][], int n, int m)
    {
        for(int i = 0;i < n;i++)
        {
            for(int j = 0;j < m;j++)
            {
                a[i][j] = ni();
            }
        }
    }
    //input two dimentional long array
    void lda(long a[][], int n, int m)
    {
        for(int i = 0;i < n;i++)
        {
            for(int j = 0;j < m;j++)
            {
                a[i][j] = nl();
            }
        }
    }
    //input two dimensional double array
    void dda(double a[][], int n, int m)
    {
        for(int i = 0;i < n;i++)
        {
            for(int j = 0;j < m;j++)
            {
                a[i][j] = nd();
            }
        }
    }
    //convert string to integer
    int stoi(String s){
        return Integer.parseInt(s);
    }
    //convert string to double
    double stod(String s){
        return Double.parseDouble(s);
    }
    //find minimum in a long array
    long lmin(long a[])
    {
        long min = Long.MAX_VALUE;
        for(int i = 0;i < a.length;i++)
        {
            if(min > a[i])
                min = a[i];
        }
        return min;
    }
    //find minimum in a integer array
    int imin(int a[])
    {
        int min = Integer.MAX_VALUE;
        for(int i = 0;i < a.length;i++)
        {
            if(min > a[i])
                min = a[i];
        }
        return min;
    }
    //find maximum in a long array
    long lmax(long a[])
    {
        long max = Long.MIN_VALUE;
        for(int i = 0;i < a.length;i++)
        {
            if(max < a[i])
                max = a[i];
        }
        return max;
    }
    //find maximum in an integer array
    int imax(int a[])
    {
        int max = Integer.MIN_VALUE;
        for(int i = 0;i < a.length;i++)
        {
            if(max < a[i])
                max = a[i];
        }
        return max;
    }
    //check whether an element is present in an integer array by binary search
    boolean ibs(int a[], int toFind)
    {
        Arrays.sort(a);
        int min = 0;
        int max = a.length-1;
        boolean found = false;

        while(min <= max && !found)
        {
            int mid = min + (max-min)/2;
            if(a[mid] == toFind)
            {
               found = true;
            }
            else if(toFind > a[mid])
            {
                min = mid+1;
            }
            else
            {
                max = mid-1;
            }

        }
        return found;
    }
    //check whether an element is present in a long array
    boolean lbs(long a[], long toFind)
    {
        Arrays.sort(a);
        int min = 0;
        int max = a.length-1;
        boolean found = false;

        while(min <= max && !found)
        {
            int mid = min + (max-min)/2;
            if(a[mid] == toFind)
            {
               found = true;
            }
            else if(toFind > a[mid])
            {
                min = mid+1;
            }
            else
            {
                max = mid-1;
            }

        }
        return found;
    }

}