Prime Number

Time Limit : 1 sec, Memory Limit : 65536 KB
Japanese version is here

Prime Number

Write a program which reads an integer n and prints the number of prime numbers which are less than or equal to n. A prime number is a natural number which has exactly two distinct natural number divisors: 1 and itself. For example, the first four prime numbers are: 2, 3, 5 and 7.

Input

Input consists of several datasets. Each dataset has an integer n (1 ≤ n ≤ 999,999) in a line.

The number of datasets is less than or equal to 30.

Output

For each dataset, prints the number of prime numbers.

Sample Input

10
3
11

Output for the Sample Input

4
2
5

Source: PC Koshien 2003 , All-Japan High School Programming Contest, Aizu-Wakamatsu, Japan, 2003
http://www.pref.fukushima.jp/pc-concours/