#!/usr/bin/perl

while(<>){
    chop;
    $samp = $_;
    push(@data, $samp);
    $tot+=$samp;
    $ct++;
}

$mean = $tot/$ct;

foreach $d (@data){
    $dd = $d-$mean;
    $sqtot += $dd*$dd;
}

print sqrt($sqtot/$ct), "\n";