<?php
[$a,$b,$c,$d,$e] = explode(" ",trim(fgets(STDIN)));
$num = $a * ($b-$c);
$count = 0;

for ($i = 1; $i <= $num; $i++) {
     if ($i % 10 == 0 && $e <= $d) {
         $count += $d-$e;
     }elseif ($i % 10 == 0 && $e > $d) {
         $count += $d;
     }else{
         $count += $d;
     }
}

echo $count;

?>