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.Linq;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine();
            var list = line.Split(' ').Select(x => int.Parse(x)).ToArray();

            var a = list[0];
            var b = list[1];
            var c = list[2];
            var k = list[3];

            var result = 0;

            for (var i = 0; i < k; i++)
            {
                if (a > 0)
                {
                    result++;
                    a--;
                }
                else if (b > 0)
                {
                    b--;
                }
                else if (c > 0)
                {
                    result--;
                    c--;
                }
            }

            Console.WriteLine(result);
        }
    }
}