get();
my @x = get().split(' ').map({.Int}).sort({ $^a <=> $^b });

for 1..@x.end {
  @x[$_-1] = @x[$_] - @x[$_-1];
}

my $ans;
for 0..@x.end-2 {
  if @x[$_] != @x[$_+1] || @x[$_] == 0 {
    $ans = 'NO';
    last;
  }
  $ans = 'YES';
}

say $ans;