<?php

$handle = fopen ("php://stdin", "r");
function howManyGames($p, $d, $m, $s) {
    $stillBuyingGames = true;
    $gamesBought = 0;
    while ($stillBuyingGames) {
        $saleCost = $p - ($gamesBought * $d);
        $gameCost =  (  $saleCost > $m) ? $saleCost : $m;
        $s -= $gameCost;
        if ($s < 0) {
            return $gamesBought;
        }
        $gamesBought++;
    }
    // Return the number of games you can buy
}

fscanf($handle, "%i %i %i %i", $p, $d, $m, $s);
$answer = howManyGames($p, $d, $m, $s);
echo $answer . "\n";

?>