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: Wrong Answer)

using System;
using System.Linq;

namespace _167_b
{
    internal class EasyLinearProgramming
    {
        private static void Main(string[] args)
        {
            var abck = Console.ReadLine()?.Split(" ").Select(long.Parse).ToList();
            if (abck == null) return;

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

            var remain = k;
            long sum = 0;

            if (remain > a)
            {
                remain -= a;
                sum += a * 1;
            }
            else
            {
                sum += a * 1;
                Console.WriteLine(sum);
                return;
            }

            if (remain > b)
            {
                remain -= b;
                sum += b * 0;
            }
            else
            {
                Console.WriteLine(sum);
                return;
            }

            sum += remain * -1;
            Console.WriteLine(sum);
        }
    }
}