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;
public class Hello{
    public static void Main(){
        // Aは１　Bは０　Cは－１　Kは枚数
        int A = 0,B = 0,C = 0,Ks = 0;
        
        int check = 0;
        
        string card = Console.ReadLine();
        var dest = card.Split(new Char[] {' '},StringSplitOptions.RemoveEmptyEntries);
        
        A = int.Parse(dest[0]);
        B = int.Parse(dest[1]);
        C = int.Parse(dest[2]);
        Ks = int.Parse(dest[3]);
        
        while (Ks != 0)
        {
            if(A != 0)
            {
                A--;
                check++;
                Ks--;
            }
            else if(B != 0)
            {
                B--;
                Ks--;
            }
            else if(C != 0)
            {
                C--;
                check--;
                Ks--;
            }
        }
        Console.WriteLine(check);
        
        
    }
}