N = int(input())

is_prime = [True] * (N + 1)
mobius = [1] * (N + 1)

is_prime[0] = is_prime[1] = False
mobius[0] = 0
mobius[1] = 1

for p in range(2, N + 1):
    if not is_prime[p]:
        continue

    mobius[p] = -mobius[p]

    for i in range(2 * p, N + 1, p):
        is_prime[i] = False

        if i % (p**2) == 0:
            mobius[i] = 0
        else:
            mobius[i] = -mobius[i]


print(sum(mobius))