class Eratosthenes:
    def __init__(self, n):
        self.isPrime = [True]*(n+1)
        self.isPrime[0], self.isPrime[1] = False, False
        self.mobius = [1]*(n+1)
        for i in range(2, n+1):
            if self.isPrime[i]:
                self.mobius[i] = -1
                for j in range(i*2, n+1, i):
                    self.isPrime[j] = False
                    if j//i%i == 0:
                        self.mobius[j] = 0
                    else:
                        self.mobius[j] *= -1

N = int(input())

E = Eratosthenes(N)
print(sum(E.mobius[1:]))