#!/usr/bin/perl -w
use strict;


open(FH,"$ARGV[0]") or die;
my @temp=<FH>;
close FH;
my $mean = Mean (\@temp);
my $variance = variance(\@temp);
print "$variance\n";

sub sum
{
        my ($arrayref) = @_;
        my $result;
        foreach(@$arrayref) { $result+= $_; }
        return $result;
}

sub Mean {
    my ($arrayref) = @_;
    my $result;
    foreach (@$arrayref) { $result += $_ }
    return $result / @$arrayref;
}


sub variance
{

        return (sum map { ($_ - $mean)**2 } @_) / $#_;
}