use strict;
use warnings;
my %edges;
while (<>) {
	/(\w+)-(\w+)/;
	$edges{$1} //= [];
	$edges{$2} //= [];
	push @{$edges{$1}}, $2;
	push @{$edges{$2}}, $1;
}
my $paths = 0;
my @queue = (['start']);
while (@queue) {
	my @path = @{shift @queue};
	my %visited = map { $_ => 1 } @path;
	for (@{$edges{$path[0]}}) {
		if ($_ eq 'end') {
			$paths++;
		} elsif (/[a-z]/ && $visited{$_}) {
			next;
		} else {
			my @next = ($_, @path);
			push @queue, \@next;
		}
	}
}
print "$paths\n";