Factorial

Score: 93.12 (pass)

#!perl -l
$n=pop;$p=1;for($i=1;$i<=$n;++$i){$f=$i;while($f%5==0){$f/=5;$p/=2}$p=$p%1e5*$f}print$p%10

Score: 121.11 (pass)

#!perl -l
($n)=@ARGV;$prod=1;for($i=1;$i<=$n;++$i){$f=$i;while ($f%5==0){$f/=5;$prod/=2;}$prod=($prod%100000)*$f}print $prod%10;