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 ABC167B {
	private static void Main(string[] args) {
		var inputs = ReadIntsAsArray();
		var a = inputs[0];
		var b = inputs[1];
		var c = inputs[2];
		var k = inputs[3];

		var answer = Math.Min(a, k) - Math.Min(c, Math.Max(0, k - a - b));
		Console.WriteLine(answer);
	}

	private static int[] ReadIntsAsArray() => Console.ReadLine().Trim().Split().Select(x => int.Parse(x)).ToArray();
}