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.*;
 
public class Main { 
    public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		long b = sc.nextLong();
		long c = sc.nextLong();
		long k = sc.nextLong();
		long ans = 0;
		if(k<a){
			ans += k*1;
			System.out.println(ans);
			return;
		} else {
			ans += a*1;
			k -= a;
		}
		if(k<b){
			ans += k*0;
			System.out.println(ans);
			return;
		} else {
			ans += b*0;
			k -= b;
		}
		if(k<c){
			ans += k*(-1);
			System.out.println(ans);
			return;
		} else {
			ans += c*(-1);
			k -= c;
		}
		System.out.println(ans);
	}
}