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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


    class Program
    {
        static void Main(string[] args)
        {
            string[] Input = Console.ReadLine().Split(' ');
            int A = int.Parse(Input[0]);
            int B = int.Parse(Input[1]);
            int K = int.Parse(Input[3]);
            int count = 0;
            
            if(K == A){
                count = A;
            }
            else if(K < A){
                count = A - K;
            }else{
                count = A;
                K -= A;
                if(K > B){
                    K -= B;
                    if(K <= 0){
                    count -= K ;
                    }
                }
            }
                Console.WriteLine(count);
            
        }
    }