<?php

$guestsCount = intval(readline());
$couvertPrice = intval(readline());
$budget = floatval(readline());

$cakePrice = $budget * 0.10;

if ($guestsCount >= 10 && $guestsCount <= 15){
    $couvertPrice *= 0.85;
} else if ($guestsCount > 15 && $guestsCount <= 20){
    $couvertPrice *= 0.80;
} else if ($guestsCount > 20){
    $couvertPrice *= 0.75;
}
$totalPrice = ($guestsCount * $couvertPrice) + $cakePrice;

if ($budget >= $totalPrice){
    $diff = number_format ($budget - $totalPrice, 2, ".", " ");
    echo "It is party time! $diff leva left.";
}else {
    printf ("No party! %0.2f leva needed.",abs ($totalPrice - $budget));
}