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 Kotlin (1.3.71) (judge verdict: Wrong Answer)

import java.util.*

fun main(args: Array<String>) {
  val sc = Scanner(System.`in`)
  val a = sc.nextInt()
  val b = sc.nextInt()
  val c = sc.nextInt()
  val k = sc.nextInt()

  println(abc167b(a, b, c, k))
}

private fun abc167b(a: Int, b: Int, c: Int, k: Int): Int {
  val ka = k - a
  if (ka <= 0) return a
  val kab = ka - b
  if (kab <= 0) return a

  return a - kab
}