n = int(input())

vis = [0] * 1000010
primes = [0] * 1000010
##cnt = 0 
##
##for i in range(2, n+1):
##    if vis[i] == 0:
##        flag = i
##        cnt += 1
##        while flag * i <= n: vis[flag * i] = 1; flag += 1;
##
##print(cnt)

#线形筛
'''
if i % primes[j] == 0: break
我们希望每个合数被最小质因子筛除
break的原因是此时pj是i的最小质因子，那么下一个pj*i筛的合数的最小质因子一定不是pj
'''
cnt = 0
for i in range(2, n+1):
    if not vis[i]:
        cnt += 1
        primes[cnt] = i
    for j in range(1, cnt+1):
        if primes[j] > n//i: break
        vis[primes[j] * i] = 1
        if i % primes[j] == 0: break

print(cnt)