<?php
error_reporting(-1);


function bank($percent, $commission, $deposit, $monthlyPayment){
	for ($i = 0; $i < 99; $i ++){
	$deposit = $deposit * $percent + $commission - $monthlyPayment;
	if($deposit <= 0){
		break;
	}
	return $i;
}
	

$creditSum = 39999;
$monthlyPayment = 5000;
$month =  bank(1.04, 500, $creditSum, $monthlyPayment);