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: Time Limit Exceeded)

using System;
using System.Linq;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] ABCK = Console.ReadLine().Trim().Split(' ').Select(s => Convert.ToInt32(s)).ToArray();
            int sum = 0;
            while (ABCK[3] > 0)
            {
                if (ABCK[0] > 0)
                {
                    sum += 1;
                    ABCK[0]--;
                }
                else if (ABCK[1] > 0)
                {
                    ABCK[1]--;
                }
                else
                {
                    sum += -1;
                    ABCK[2]--;
                }

                ABCK[3]--;
            }

            Console.WriteLine(sum);
        }
    }
}