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[] input = Console.ReadLine().Split(' ');
        long result = 0;
        var a = long.Parse(input[0]);
        var b = long.Parse(input[1]);
        var c = long.Parse(input[2]);
        var k = long.Parse(input[3]);
        if (k <= a)
        {
            result = k;
        }
        else if (k <= a + b)
        {
            result = a;
        }
        else
        {
            result = a - (k - a - b);
        }
        Console.WriteLine(result);
    }
}