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.InputStream;
import java.io.PrintStream;
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    resolve(System.in, System.out);
  }

  static void resolve(InputStream is, PrintStream pw) {
    Scanner sc = new Scanner(is);
    int a = Integer.parseInt(sc.next());
    int b = Integer.parseInt(sc.next());
    int c = Integer.parseInt(sc.next());
    int k = Integer.parseInt(sc.next());
    int remainK = k;

    int numA = Math.min(remainK, a);
    int ans = 0;
    ans += numA;
    remainK -= numA;
    if (remainK == 0) {
      pw.println(ans);
      return;
    }
    int numB = Math.min(remainK, b);
    remainK -= numB;
    if (remainK == 0) {
      pw.println(ans);
      return;
    }
    ans -= remainK;
    pw.println(ans);
  }
}