my $n=get.Int;
my Set $se=(0..9).Set;
for ^$n {
  my @parts=get.words;
  my $r=@parts[*-1];
  my Set $a=@parts[0..*-2].map(*.Int).Set;
  if $r eq "YES" {
    $se = $se ∩ $a;
  } else{
    $se = $se (-) $a;
  }
}
+$se==1 or die "Assertion failed: Invalid input encountered";
say $se.keys[0];