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: Wrong Answer)

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        main.run();
    }
    
    // 変数一覧
    long a;
    long b;
    long c;
    long k;
    long ans;

    public void run() {
        // 入力情報取得
        Scanner sc = new Scanner(System.in);
        a = sc.nextLong();
        b = sc.nextLong();
        c = sc.nextLong();
        k = sc.nextLong();
        sc.close();

        // 解答処理
        solve();
    }
    
    private void solve() {
        long rem = k;
        if (a <= rem) {
            ans = a;
            rem -= a;
        } else {
            ans = a;
            rem = 0;
        }
        if (b <= rem && rem > 0) {
            rem -= b;
        } else {
            rem = 0;
        }
        if (rem > 0) {
            ans -= rem;
        }
        System.out.println(ans);
    }
}