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;

class Program
{
	static void Main(string[] args)
	{
		string[] strInput = Console.ReadLine().Split(' ');
		int a = int.Parse(strInput[0]);
		int b = int.Parse(strInput[1]);
		int c = int.Parse(strInput[2]);
		int k = int.Parse(strInput[3]);

		int result = 0;
		if (a > k)
		{
			result = k;
			Console.WriteLine(result);
			return;
		}
		else
		{
			result = a;
			k -= a;
		}

		if (b > k)
		{
			Console.WriteLine(result);
			return;
		}

		k -= b;
		result -= k;
	
		Console.WriteLine(result);
		return;
	}
}