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

$line = explode(' ', trim(fgets(STDIN)));

$plus1 = $line[0];
$plus0 = $line[1];
$minus1 = $line[2];
$pick = $line[3];
$result = 0;

if($pick > 0 && $pick-$plus1 >= 0)
{
  $result += $plus1;
  $pick -= $plus1;
}else{
  $result += $pick;
  $pick = 0;
}

if($pick > 0 && $pick-$plus0 >= 0)
{
  $pick -= $plus0;
}else{
  $pick = 0;
}

if($pick > 0 && $pick-$minus1 >= 0)
{
  $result -= $minus1;
  $pick -= $minus1;
}else{
  $result -= $pick;
  $pick = 0;
}

echo $result . PHP_EOL;