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 PHP (7.4.4) (judge verdict: Time Limit Exceeded)

<?php
fscanf(STDIN, "%d %d %d %d", $a, $b, $c, $k);
$sum = 0;

while ($k > 0) {
    if ($a > 0) {
        $sum += 1;
        $a -= 1;
        $k -= 1;
        continue;
    }
    if ($b > 0) {
        $sum += 0;
        $b -= 1;
        $k -= 1;
        continue;
    }
    if ($c > 0) {
        $sum -= 1;
        $c -= 1;
        $k -= 1;
        continue;
    }

    $k -= 1;
}
echo $sum;