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 input = new Scanner(System.in);
    
    long a = input.nextLong();
    long b = input.nextLong();
    long c = input.nextLong();
    long k = input.nextLong();
    
    int ans = 0;
    if (k <= a) {
      System.out.println(k);
      return;
    }
    
    ans += a;
    k -= a;
    if (k <= b) {
      System.out.println(ans);
      return;
    }
    k -= b;
    ans -= k;
    
    System.out.println(ans);
  }
}