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.Collections.Generic;
using System.IO;
using System.Linq;

namespace AtCorder
{
    public static class Program
    {
        static public void Main(string[] args)
        {
            var input = Console.ReadLine().Split().Select(long.Parse).ToArray();
            //var ans = 0;

            if (input[0] >= input[3])
            {
                Console.WriteLine(input[0].ToString());
            }
            else if ((input[0] + input[1]) >= input[3])
            {
                Console.WriteLine(input[0].ToString());
            }
            else if (((input[0] + input[1] + input[2]) >= input[3]))
            {
                var num = input[0] + input[1];
                input[3] = input[3] - num;
                num = input[0] - input[3];
                Console.WriteLine(num.ToString());
            }




            //for (var i = input[3]; i > 0; i--)
            //{
            //    if (input[0] > 0)
            //    {
            //        ans = ans + 1;
            //        input[0] = input[0] - 1;
            //    }
            //    else if (input[1] > 0)
            //    {
            //        ans = ans + 0;
            //        input[1] = input[1] - 1;
            //    }
            //    else
            //    {
            //        ans = ans - 1;
            //        input[2] = input[2] - 1;

            //    }
            //}

        }
    }
}