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.*;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    long a = sc.nextLong();
    long b = sc.nextLong();
    long c = sc.nextLong();
    long k = sc.nextLong();
    sc.close();

    long sum = 0;

    if (a <= k) {
      sum += a * 1;
      k -= a;
    } else {
      System.out.println(k);
      return;
    }
    if (k <= 0) {
      System.out.println(sum);
      return;
    }

    if (b <= k) {
      sum += b * 0;
      k -= b;
    } else {
      System.out.println(sum);
      return;
    }
    if (k <= 0) {
      System.out.println(sum);
      return;
    }

    if (c <= k) {
      sum += c * -1;
      k -= c;
    } else {
      sum += k * -1;
    }
    System.out.println(sum);
  }
}