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)
	{
		string[] input = Console.ReadLine().Split(' ');
		int a = int.Parse(input[0]);
		int b = int.Parse(input[1]);
        int c = int.Parse(input[2]);
        int k = int.Parse(input[3]);
        int sum = 0;
        int remain = k;
        if(a >= k) {
            Console.WriteLine(k);
            return;
        }
        else if(a != 0){
            sum += a;
            remain -= a;
        }
        if(b >= remain){
            Console.WriteLine(sum);
            return;
        }
        else if(b != 0){    
            remain -= b;
        }
        
        sum -= remain;
        Console.WriteLine(sum);
	}
}