l = int(input())
first = 2
cnt = 0
i = 3
while i < l+1:
j = 2
while j <= i**0.5:
if i % j == 0:
break
if j == 2:
j += 1
else:
j += 2
else:
if i - first == 2:
cnt += 1
first = i
i += 2
print(cnt)
XiLong Liu的博客原题链接 import math def tell_prime_number(number): if number > 1: for i in range(2, int(math.sqrt... 最后借鉴大牛博客,最后得以解决,尊重原创,所以这里将大牛代码贴在下面,供诸君学习: 1007素数对猜想优化