import math
def f(x):
if x == 1: return 0
global cnt
s = int(math.sqrt(x))
for i in range(2, s + 1):
cnt += 1
if x % i == 0: return 1
return 2
if __name__ == '__main__':
cnt = 0
n = int(input())
for i in range(1, n + 1): f(i)
print(cnt)
每次给定 n, 请求出 cnt 的值。