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;
namespace kozaiyApp
{
    public class B
    {
        static void Main()
        {
            string[] input = Console.ReadLine().Split(' ');
            int A = int.Parse(input[0]); // 1
            int B = int.Parse(input[1]); // 0
            int C = int.Parse(input[2]); // -1
            int K = int.Parse(input[3]); // 選ぶ枚数

            int ans = 0;

            if (A >= K)
            {
                Console.WriteLine(K);
            }
            else
            {
                K = K - A;
                ans += A;
                if (B >= K)
                {
                    Console.WriteLine(ans);
                }
                else
                {
                    K = K - B;
                    ans -= K;
                    Console.WriteLine(ans);
                }
            }
        }
    }
}