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 = str_replace('　', ' ', fgets(STDIN));
$line = explode(' ', $input);

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

if(full_up_with_ab($A, $B, $K)){
  echo $A;
}else {
  if(full_up_with_abc($A, $B, $C, $K)){
    $C = $K - ($A + $B);
  }
  echo $A - $C; 
}

function full_up_with_ab($A, $B, $K){
  return ($A + $B) >= $K;
}

function full_up_with_abc($A, $B, $C, $K){
  return ($A + $B + $C) >= $K;
}