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 ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            var solver = new Solver();
            solver.Calc();
        }
    }

    public class Solver
    {
        public struct AB
        {
            public int A;
            public int B;
        }
        public void Calc()
        {
            var p = Console.ReadLine().Split().Select(x => long.Parse(x)).ToArray();
            var A = p[0];
            var B = p[1];
            var C = p[2];
            var K = p[3];

            var remain = K;
            long sum = 0;
            if (A >= remain)
            {
                Console.WriteLine(remain);
                return;
            }
            else
            {
                remain = remain - A;
                sum = A;

                if (B >= remain)
                {
                    Console.WriteLine(sum);
                    return;
                }
                else
                {
                    remain = remain - B;
                    Console.WriteLine(sum - remain);
                    return;
                }

            }


        }


    }

}