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.Scanner;

/**
 * Easy Linear Programming.
 */
public class Main {
    public static void main(String[] args) {
        var scanner = new Scanner(System.in);
        var a = scanner.nextInt();
        var b = scanner.nextInt();
        var c = scanner.nextInt();
        var k = scanner.nextInt();

        var sum = Math.min(k, a);
        var remaining = Math.min(k - a - b, c);
        sum += remaining > 0 ? -1 * remaining : 0;
        System.out.println(sum);
    }
}