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;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            var ABCK = GetLongNumArray();
            var A = ABCK[0];
            var B = ABCK[1];
            var C = ABCK[2];
            var K = ABCK[3];
            long max = 0;

            if (A <= K)
            {
                max = A;
                K = K - A;
            }
            else
            {
                max = K;
                Console.WriteLine(max);
                return;
            }

            if (B <= K)
            {
                K = K - B;
            }
            else
            {
                Console.WriteLine(max);
                return;
            }

            if (K != 0)
            {
                max = max - K;
                Console.WriteLine(max);
                return;
            }

            Console.WriteLine(max);



            //for (int i = 0; i < ABCK[3]; i++)
            //{
            //    if (A != 0)
            //    {
            //        max++;
            //        A = A - 1;
            //        continue;
            //    }

            //    if (B != 0)
            //    {
            //        B = B - 1;
            //        continue;
            //    }

            //    if (C != 0)
            //    {
            //        max--;
            //        C = C - 1;
            //        continue;
            //    }
            //}

            //Console.WriteLine(max);
        }

        private static long[] GetLongNumArray()
        {
            var input = Console.ReadLine().Split(' ');
            return input.Select(x => long.Parse(x)).ToArray();
        }

        private static long GetLongNum()
        {
            return long.Parse(Console.ReadLine());
        }

        private static string[] GetStringArray()
        {
            return Console.ReadLine().Split(' ');
        }

        private static string GetString()
        {
            return Console.ReadLine();
        }
    }
}