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.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class Main {

  static int a, b, c, k, ans;

  public static void main(String[] args) throws Exception {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    PrintWriter out = new PrintWriter(System.out);

    String[] in = br.readLine().split(" ");
    a = Integer.parseInt(in[0]);
    b = Integer.parseInt(in[1]);
    c = Integer.parseInt(in[2]);
    k = Integer.parseInt(in[3]);

    /*
    =====templates=====
    ===inputs===
    static int n;
    in = br.readLine().split(" ");
    int[] a = Stream.of(in).mapToInt(Integer::parseInt).toArray();

    int n = Integer.parseInt(in[0]);
    long n = Long.parseLong(in[0]);
    int[] a = Stream.of(in).mapToInt(Integer::parseInt).toArray();

    ===outputs===
    PrintWriter out = new PrintWriter(System.out);
    out.println(ans);
    out.flush();
    */

    br.close();

    ans = Math.min(a, k);
    k -= a + b;
    if(k > 0) ans -= k;

    out.println(ans);

    out.flush();

  }
}