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.abc167.b
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] inputArray = getIntParams();
            int A = inputArray[0];
            int B = inputArray[1];
            int C = inputArray[2];
            int K = inputArray[3];

            int ret = 0;
            if (K <= A)
            {
                ret = K;
            }
            else
            {
                ret = A;
                K -= A;
                if (K > B)
                {
                    K -= B;
                    if (K <= C)
                    {
                        ret -= K;
                    }
                }
            }
            Console.WriteLine(ret);
        }

        static int getIntParam()
        {
            return int.Parse(Console.ReadLine());
        }
        static int[] getIntParams()
        {
            return Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray();
        }
        static long getLongParam()
        {
            return long.Parse(Console.ReadLine());
        }
        static long[] getLongParams()
        {
            return Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();
        }
        static string getStringParam()
        {
            return Console.ReadLine();
        }
        static string[] getStringParams()
        {
            return Console.ReadLine().Split(' ');
        }
        static decimal getDecimalParam()
        {
            return decimal.Parse(Console.ReadLine());
        }
        static decimal[] getDecimalParams()
        {
            return Console.ReadLine().Split(' ').Select(i => decimal.Parse(i)).ToArray();
        }
    }
}