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# (Mono-mcs 6.8.0.105) (judge verdict: Wrong Answer)

using System;
using System.Linq;

namespace Paiza_D155
{
    class Program
    {
        static void Main(string[] args)
        {
            //int num = int.Parse(Console.ReadLine());
            //var input = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            //int limit = input[0];
            //int gFee = input[1];
            //int sFee = input[2];

            //int ans = 0;
            //if (num >= limit) ans = gFee * num;
            //else ans = sFee * num;

            //Console.WriteLine(ans.ToString());

            //var orgS = Console.ReadLine().ToCharArray();
            //var newS = Console.ReadLine().ToCharArray();

            //bool isOK = true;
            //int cnt = 0;
            //foreach(var c in orgS)
            //{
            //    if (!c.Equals(newS[cnt]))
            //    {
            //        isOK = false;
            //        break;
            //    }

            //    cnt++;
            //}

            //if (isOK) Console.WriteLine("Yes");
            //else Console.WriteLine("No");


            var input = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            int A = input[0];
            int B = input[1];
            int C = input[2];
            int K = input[3];


            int ans = A;
            K -= A;

            if (0 != K) 
            {
                K -= B;
            }

            if (0 != K)
            {
                ans -= K;
            }

            Console.WriteLine(ans.ToString());
        }
    }
}