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)

public class Hello{
    public static void Main(){
        
        string line1 = System.Console.ReadLine();
        string[] array = line1.Split(' ');
        
        int a = int.Parse(array[0]);
        int b = int.Parse(array[1]);
        int c = int.Parse(array[2]);
        int k = int.Parse(array[3]);
        
        int result = 0;
        
        if(a > k)
        {
            result = k;
        }
        else
        {
            result += a;
            k -= a;
            
            if(k > 0)
            {
                if(b <= k)
                {
                    k -= b;
                    
                    if(k > 0)
                    {
                        result -=k;
                    }
                }
                
                
            }
        }
        System.Console.WriteLine(result);
    }
}