Problem:
Score : 200 points

Problem Statement

We have A cards, each of which has an integer 1 written on it. Similarly, we also have B cards with 0s and C cards with -1s.

We will pick up K among these cards. What is the maximum possible sum of the numbers written on the cards chosen?

Constraints

All values in input are integers.

0 \leq A, B, C

1 \leq K \leq A + B + C \leq 2 \times 10^9

Input

Input is given from Standard Input in the following format:

A B C K

Output

Print the maximum possible sum of the numbers written on the cards chosen.

Sample Input 1

2 1 1 3

Sample Output 1

2

Consider picking up two cards with 1s and one card with a 0.
In this case, the sum of the numbers written on the cards is 2, which is the maximum possible value.

Sample Input 2

1 2 3 4

Sample Output 2

0

Sample Input 3

2000000000 0 0 2000000000

Sample Output 3

2000000000

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.*;
        import java.math.BigInteger;
        import java.util.Arrays;
        import java.util.Scanner;
public class Main {
    public static int gcd(int a,int b){
        if(b==0)
            return a;
        int v=a%b;
        return gcd(b,v);
    }
    public static StreamTokenizer in;
    static {
        try{
            in = new StreamTokenizer(new BufferedReader(new InputStreamReader(new BufferedInputStream(System.in))));
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    public static int nextInt() throws IOException{ in.nextToken(); return (int)in.nval; }
    public static void main(String[] args) throws IOException{
        Scanner sc=new Scanner(new BufferedInputStream(System.in));
        int a=nextInt();
        int b=nextInt();
        int c=nextInt();
        int k=nextInt();
        long all=0;
        if(k<a)
            all=k;
        else{
            all+=a;
            k-=a;
            if(k>b)
                all-=(k-b);
        }
        System.out.print(all);
    }
}