my ($n, $p) = get.words;

put solve($n.Int, $p.Rat);

sub solve(Int $n, Rat $p) {
  my $p2 = 1.0 - $p;
  my @s = gather for 1..$n+1 { take 1.0 };
  my $ans = 0.0;
  for 2..$n -> $i {
    $ans = $ans + @s[$i];
    for $i*2,$i*3...$n -> $j {
      @s[$j] = @s[$j] * $p2;
    }
  }
  return $ans;
}