print bin2dec("1110010101011101111011110110101010111");


# Calculate a (arbitrarily large) decimal number from its
# binary representation
#
sub bin2dec
{
	my ($str) = @_;
	my $ret = "";
	
	$ret = mul2($ret, $_) 
		foreach split(//, $str);
	
	return $ret;
}


# Given a (arbitrarily large) decimal number N as a string, 
# returns 2N or 2N+1
#
sub mul2
{
	my ($str, $add_one_f) = @_;
	defined($add_one_f) or $add_one_f = 0;
	my $ret = "";
		
	foreach (my $i = length($str) - 1; $i >= 0; --$i)
	{
		my $c = substr($str, $i, 1) * 2;
		$c += 1 if ($add_one_f);
		
		$ret = ($c % 10) . $ret;
		$add_one_f = ($c >= 10);
	}
	
	return $add_one_f ? '1' . $ret : $ret;
}