<?php

$handle = fopen ("php://stdin", "r");
function howManyGames($p, $d, $m, $s) {
    $times =0 ;
    $currentmoney =$s ;
    $currentrate = $p ;
    while($currentmoney>=$currentrate){
        $currentmoney= $currentmoney-$currentrate;
        if(($currentrate-$d)>$m){
            $currentrate = $currentrate- $d;
            $times++;
        }else{
            $currentrate = $m;
             $times++;
        }
    }
    return $times;
}

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

?>