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;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC167_B
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = Console.ReadLine()
                .Split(' ')
                .Select(str => int.Parse(str))
                .ToArray();

            int A = arr[0];
            int B = arr[1];
            int C = arr[2];
            int K = arr[3];

            if (K <= A)
            {
                Console.WriteLine(K);
            }
            else if (A < K && K <= A + B)
            {
                Console.WriteLine(A);
            }
            else if (A + B < K && K <= A + B + C) {
                Console.WriteLine(A - (K - (A + B)));
            }
            Console.ReadLine();
        }

    }
}