#!/usr/bin/perl
use strict;
use warnings;

my @n;
while(<STDIN>)
{
  chomp;
  $_ or last;
  /^\d+(\.\d+)?/ or die("NO Number");
  push(@n,$_+0);
}

my $s=0; map{$s+=$_}@n; $s/=@n;
print "Durchschitt: $s\n";