<?php

$lenght = floatval(readline());
$width = floatval(readline());
$sideWardrobe = floatval(readline())*100;

$size = ($lenght*100)*($width*100);
$wardrobe = $sideWardrobe * $sideWardrobe;
$bench = $size/10;
$freeSpace = $size - ($wardrobe+$bench);
$numberOfDancer = $freeSpace / (40 + 7000);

echo round($numberOfDancer);