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: Wrong Answer)

<?php
$input = fgets(STDIN);
$array = explode(' ', $input);

$count_num1 = $array[0];
$count_num0 = $array[1];
$count_numm1 = $array[2];
$count_all = $array[3];

$max_sum = 0;

if ($count_num1 + $count_num0 >= $count_all) {
    $max_sum = $count_num1;
} else {
    $max_sum += $count_num1;
    $m1 = $count_all - ($count_num1 + $count_num0);
    $max_sum += (-1) * $m1;
}

echo $max_sum;