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;
public class Main {
	public static void main (String[] args) {

//	パターン1（Aから順番に使って足していく）
//	変数を読み込む
		Scanner sc = new Scanner(System.in);
		int A = sc.nextInt();
		int B = sc.nextInt();
		int C = sc.nextInt();
		int K = sc.nextInt();

		int total = 0;  //合計を入れる変数

//	Aから順に、合計K枚になるまで足していく
		if(A >= K) {
			total = K;
			System.out.println(total);
			return;
		}
		else {  //A＜Kの場合は続く
			total = A;
		}

		if(B < K-A) {  //B<=K-AならK-A-B枚分引く
			total -= K-A-B;
			System.out.println(total);
		}
		else {  //B>K-Aならそのまま表示
			System.out.println(total);
			return;
		}
	}
}