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;

namespace abc167b
{
    class Program
    {
        static void Main(string[] args)
        {
            //==========================================================================================================================
            //1) input
            List<decimal> input = Console.ReadLine().Split(' ').Select(decimal.Parse).ToList();
            decimal a = input[0];//1
            decimal b = input[1];//0
            decimal c = input[2];//-1
            decimal k = input[3];

            decimal output = 0;


            if (k <= a)
            {
                output = k;
            }
            else if (k <= a + b)
            {
                output = a;
            }
            else
            {
                output = a + (k - (a + b)) * (-1);

            }
            //==========================================================================================================================
            //2) output

            Console.WriteLine(output);
        }
    }
}