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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
		
		var x = Console.ReadLine().Split().Select(y => int.Parse(y)).ToArray();
		int a = x[0];
		int b = x[1];
		int c = x[2];
		int k = x[3];
		
		if(k<=a){
			Console.WriteLine(k);
		}else if(k<=a+b){
			Console.WriteLine(a);
		}else{
			Console.WriteLine(2*a+b-k);
		}
		
	}
}