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);

    $a_calc = 1 * $a; //1
    $hiki = $k - $a; //3
    if($hiki <= 0){
        if($a_calc <= 0){
            echo 0;
            exit;
        } else {
            echo $a_calc;
            exit;
        }
    }
    $b_calc = 0 * $b;// 0
    $hiki = $hiki - $b; //3 - 2 = 1
    if($hiki <= 0){
        if(($a_calc + $b_calc) <= 0){
            echo 0;
            exit;
        } else {
            echo $a_calc + $b_calc;
            exit;
        }
    }
    $c_calc = -1 * $c; // -3 
    $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;
            exit;
        }
    }