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;
using System.Collections;
using System.Collections.Generic;

public class AtCoder
{
    public static void Main()
    {
        var abck = Console.ReadLine().Trim().Split().Select(e=>int.Parse(e)).ToArray();
        var a = abck[0];
        var b = abck[1];
        var c = abck[2];
        var k = abck[3];

        int xa = Math.Min(a, k);
        k -= xa;
        int xb = Math.Min(b, k);
        k -= xb;
        int xc = k;
        
        var ans  = xa - xc;
        Console.WriteLine(ans);
   }
}