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;
class ss
{
  static void Main()
  {
    var n=Console.ReadLine().Split(" ");
    int a=int.Parse(n[0]);
    int b=int.Parse(n[1]);
    int c=int.Parse(n[2]);
    int k=int.Parse(n[3]);
    int sum=0;
    if(k>=a)
    {
      sum+=a;
      k-=a;
    }
    else
    {
      sum+=k;
      k=0;
    }
     if(k>=b)
      k-=b;
    else
      k=0;
     if(k>=c)
    {
      sum-=c;
    }
    else
      sum-=k;
    Console.WriteLine(sum);
      
    
   
  }
}