#!/usr/bin/perl -w

use v5.16;

my @c = split /[,\s]/, <>;

my $max;
($max = !$max || $max < $_ ? $_ : $max) for @c;

my $min_f;
for my $pos (0 .. $max) {
	my $f = 0;
	for my $c1 (@c) {
		my $dist = abs($c1 - $pos);
		$f += $dist * ($dist+1) /2;
	}
	$min_f = $f if !$min_f || $min_f > $f;
	# say "$pos $f $min_f";
}

say $min_f;
