n = read_line.to_i
is_prime = Array.new(n + 1, true)
mu = Array.new(n + 1, 1)
mu[0] = 0
2.upto(n) do |i|
  if is_prime[i]
    (i * 2).step(to: n, by: i) do |j|
      is_prime[j] = false
      mu[j] *= -1
    end
    mu[i] *= -1
    mu[i * i] = 0 if i.to_i64 * i <= n
  end
  if mu[i] == 0
    (i * 2).step(to: n, by: i) do |j|
      mu[j] = 0
    end
  end
end
puts mu.sum