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
// Your code here!

fscanf(STDIN, "%d %d %d %d", $a, $b, $c, $k);
// var_dump($k);

$sum = 0;
$zank = $k;
if($a >= $k){
    $zank -= $a;
    $sum += $a;
}
if($a <= $k){
    $zank -= $a;
    $sum += $a;
}
if($zank < $b){
    $zank -= $b;
}
if($zank >= $b){
    $zank -= $b;
}
// var_dump($zank);
if($zank >= 0){
    $sum += -$zank;
}


// var_dump($zank);
print($sum);



?>