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# (Mono-mcs 6.8.0.105) (judge verdict: Wrong Answer)


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class CF
{


    public static int[] ReadArray()
    {
        return Array.ConvertAll(Console.ReadLine().Split(' '), m => Convert.ToInt32(m));
    }

    public static int ReadInt()
    {
        return Convert.ToInt32(Console.ReadLine());
    }

    public static string ReadStr()
    {
        return Console.ReadLine();
    }

    public static long ReadLong()
    {
        return Convert.ToInt64(Console.ReadLine());
    }

    public static long[] ReadLongArray()
    {
        return Array.ConvertAll(Console.ReadLine().Split(' '), m => Convert.ToInt64(m));

    }


    public static void Main()
    {
        long[] A = ReadLongArray();

        long ans = 0;
        if (A[3] >= A[0])
            ans += A[0];

        if (A[3] - (A[1] + A[0]) > 0)
            ans -= Math.Min(A[3] - (A[1] + A[0]), A[2]);


        Console.WriteLine(ans);

    }

}