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: Accepted)

<?php

while ($stdin = fgets(STDIN)) {
    $line[] = trim($stdin);
}
foreach ($line as $key => $value) {
    $data[] = explode(' ', $value);
}

foreach ($data as &$line) {
    $line = array_map(function($val) { return (int)$val; }, $line);
}

$A = $data[0][0];
$B = $data[0][1];
$C = $data[0][2];
$K = $data[0][3];

$ans = 0;

if ($A < $K) {
    $ans += $A * 1;
    $K -= $A;
} else {
    $ans += $K * 1;
    $K -= $K;
}

if ($B < $K) {
    $ans += $B * 0;
    $K -= $B;
} else {
    $ans += $K * 0;
    $K -= $K;
}

if ($C < $K) {
    $ans += $C * -1;
    $K -= $C;
} else {
    $ans += $K * -1;
    $K -= $K;
}

printf('%d', $ans);