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.Collections.Generic;
using System.Linq;

public class Hello
{
    public static void Main()
    {
        hoge();
        //System.Console.ReadLine();
    }

    public static void hoge()
    {
        var vars = System.Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
        var a = vars[0];
        var b = vars[1];
        var c = vars[2];
        var k = vars[3];
        long sum = 0;
        if(a <= k)
        {
            sum = a;
            k -= a;
        }
        else
        {
            System.Console.WriteLine(k);
            return;
        }

        if(b <= k)
        {
            k -= b;
        }
        else
        {
            System.Console.WriteLine(sum);
            return;
        }


        if (c <= k)
        {
            sum -= c;
            k -= c;
            System.Console.WriteLine(sum);
            return;
        }
        else
        {
            System.Console.WriteLine(sum - 1 * k);
            return;
        }
    }
}