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.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long a = Long.parseLong(sc.next());
        long b = Long.parseLong(sc.next());
        long c = Long.parseLong(sc.next());   
        long k = Long.parseLong(sc.next());
        long count = 0;
        if(a <= k) {
            count += a;
            k -= a;
            if(b <= k) {
                k -= b;
                if(c <= k) {
                    count -= c;
                    k -=c;
                }else {
                    count -= k;
                    k = 0;
                }
            }else {
                k = 0;
            }
        }else {
            count = k;
            k = 0;
        }
        System.out.println(count);
    }
}