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.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Security;
using System.Xml.Serialization;

namespace AtCoderCs
{

    class Program
    {

        const int Mod = 1000000007;

        static void Main()
        {

            var args = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
            var result = 0;
            if (args[3] <= args[0])
            {

                Console.WriteLine(args[3]);

            }
            else if (args[3] <= args[1])
            {

                Console.WriteLine(args[0]);

            }
            else
            {

                Console.WriteLine(args[0] - (args[3] - (args[1] + args[0])));

            }

        }


    }
}