open(IN, "pa5c.dat") || die ("Can't open file $!\n");
        while($line = <IN>){
		chomp($line);
		++$number;
		($name, $score) = split(/:/, $line);
		
        $sum = $sum + $score;
		$avg = $sum / $number;
	
		$totd += ($score - $avg)**2;
		$std = sqrt ($totd/ $number);
}