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: Wrong Answer)

using System;

class A167_B{
  static void Main(){
    int[] Ar = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
    int A = Ar[0], B = Ar[1], C = Ar[2], K = Ar[3];
    int O = 0;
    if (A + B >= K){
      Console.WriteLine(A);
    }
    else {
      O = O + A;
      K -= (A + B);
      O -= K;
      Console.WriteLine(O);
    }
  }
}