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 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

// https://atcoder.jp/contests/abc167/tasks/abc167_b
public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ

		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 startTime = System.currentTimeMillis();

		long ans = 0L;

		if(a>=k) {
			ans = ans + 1L*k;
			System.out.println(ans);
			return;
		}else {
			ans = ans + 1L*a;
			k = k-a;
			if(b>=k) {
				System.out.println(ans);
				return;
			}else {
				k = k-b;
				if(c>=k) {
					ans = ans - 1L*k;
					System.out.println(ans);
					return;
				}else {
					ans = ans - 1L*c;
					System.out.println(ans);
					return;
				}
			}
		}
	}
}