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: Time Limit Exceeded)

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(int.Parse).ToArray();
            var ans = 0;
            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;

                }
            }
            Console.WriteLine(ans.ToString());


        }
    }
}