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)

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

    var maxVal = 0L

    // Aのカードを選択
    if (a >= k) {
        maxVal += k * 1
        print(maxVal)
        return
    } else {
        maxVal += a * 1
        k -= a
    }

    // Bのカードを選択
    if (b >= k) {
        maxVal += k * 0
        print(maxVal)
        return
    } else {
        maxVal += b * 0
        k -= b
    }

    // cのカードを選択
    maxVal += k * -1

    print(maxVal)
}