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

    if($a >= $k){
        $a = $k;
        echo $a * 1;
    }
    $hiki = $k - $a;
    $a_calc = 1 * $a;
    if($hiki <= 0){
        // if($a_calc < 0){
        //     echo 0;
        //     exit;
        // } else {
            echo $a_calc;
            exit;
        // }
    }
    $hiki = $hiki - $b;
    $b_calc = 0 * $hiki;
    if($hiki <= 0){
        // if(($a_calc + $b_calc) < 0){
        //     echo 0;
        //     exit;
        // } else {
            echo $a_calc + $b_calc;
            exit;
        // }
    }
    $c_calc = -1 * $hiki; // 
    // $hiki = $hiki - $c; // 1
    // if($hiki <= 0){
        // if(($a_calc + $b_calc + $c_calc) < 0){
        //     echo 0;
            // exit;
        // } else 
        // {
            echo $a_calc + $b_calc + $c_calc;
        // }
    // }