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: Wrong Answer)

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        int[] inputi = new int[4];
        string[] inputs = Console.ReadLine().Split(' ');
        for (int cnt = 0; cnt < inputs.Length; cnt++)
        {
            if (cnt < inputi.Length)
            {
                if (!int.TryParse(inputs[cnt], out inputi[cnt]))
                {
                    Console.WriteLine(0);
                    return;
                }
                // 0≤A,B,C
                if (cnt < 3 && inputi[cnt] < 0)
                {
                    Console.WriteLine(0);
                    return;
                }
                // 1≤K≤A+B+C
                if (cnt == 3 && (inputi[cnt] < 1 || inputi[cnt] > inputi[0] + inputi[1] + inputi[2]))
                {
                    Console.WriteLine(0);
                    return;
                }
            } else
            {
                Console.WriteLine(0);
                return;
            }
        }

        inputi[3] = inputi[3] - inputi[0];
        if (inputi[3] <= 0)
        {
            Console.WriteLine(inputi[0]);
            return;
        }
        inputi[3] = inputi[3] - inputi[1];
        if (inputi[3] <= 0)
        {
            Console.WriteLine(inputi[0]);
            return;
        }
        inputi[3] = inputi[3] - inputi[2];
        if (inputi[3] <= 0)
        {
            Console.WriteLine(inputi[0] - 1 * (inputi[2] + inputi[3]));
            return;
        }

        return;
    }
}