import sys
input = lambda :sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
ms = lambda: map(str, input().split())
mf = lambda: map(float, input().split())
li = lambda: list(mi())

def main():
    N = ii()
    def sieve(x):
        isprime = [True] * (x + 1)
        if x >= 0: isprime[0] = False
        if x >= 1: isprime[1] = False
        for i in range(2, x + 1):
            if i * i > x: break
            if not isprime[i]: continue
            for j in range(i * i, x + 1, i): isprime[j] = False
        return isprime
    n = 1_000_000
    prime = sieve(n)
    now = 1
    ans = 0
    for i in range(1, n + 1):
        if(prime[i]):
            if(now * i <= N):
                now *= i
                ans += 1
            else:
                break
    print(ans)
if __name__ == '__main__':
    main()