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;

namespace abc167_b
{
    class Program
    {
        static void Main(string[] args)
        {
            string stringAll = Console.ReadLine();
            string[] stringArray = stringAll.Split(" ");
            int add = int.Parse(stringArray[0]);
            int zero = int.Parse(stringArray[1]);
            int mainasu = int.Parse(stringArray[2]);
            int sum = int.Parse(stringArray[3]);

            int outputInt = 0;

            if(sum < add)
            {
                Console.WriteLine(sum);
                return;
            }
            else if(sum == add)
            {
                Console.WriteLine(add);
                return;
            }
            outputInt = 1 * add;
            sum -= add;

            sum -= zero;
            if (0 >= sum)
            {
                Console.WriteLine(outputInt);
                return;
            }

            int mainasuSum = 0;
            if (0 == mainasu)
            {
            }
            else if(sum < mainasu)
            {
                mainasuSum = -1 * sum;
                outputInt += mainasuSum;
            }
            else
            {
                mainasuSum = -1 * mainasu;
                outputInt += mainasuSum;
            }
            Console.WriteLine(outputInt);
            return;
        }
    }
}