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: Accepted)

// シンプルにする2つ目
// 高階関数を利用
// これはまだ早いかもなぁ

fun main (args:Array<String>){
    val (a , b , c , k) = readLine()!!.split(" ").map(String::toLong)

    val sumCount = fun(lastSelectCount: Long, sumNum: Long): (cardCount: Long, cardNum: Long) -> Long {
        var lastSelectCount = lastSelectCount
        var sumNum = sumNum
        return fun(cardCount: Long, cardNum: Long): Long {
            if (cardCount < lastSelectCount) {
                lastSelectCount -= cardCount
                sumNum += cardCount * cardNum
            } else {
                sumNum += lastSelectCount * cardNum
                lastSelectCount = 0
            }
            return sumNum
        }
    }

    val calc = sumCount(k, 0)
    calc(a, 1)
    calc(b, 0)
    print(calc(c, -1))
}