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;
class Program
{
  static void Main(string[] args)
  {
    int a, b, k;
    string[] s = Console.ReadLine().Split(' ');
    a = int.Parse(s[0]);
    b = int.Parse(s[1]);
    k = int.Parse(s[3]);
    if (k <= a)
    {
      Console.WriteLine(k);
    }
    else if (k - a < b)
    {
      Console.WriteLine(a);
    }
    else
    {
      Console.WriteLine(2 * a - k + b);
    }
  }
}