AOJ0009Prime Number

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, 7.

Input

Input consists of several datasets. Each dataset has an integer n (n ≤ 999999) in a line.

The number of datasets ≤ 30.

Output

For each dataset, prints the number of prime numbers.

Sample Input

10311

Output for the Sample Input

425

package 素数;import java.util.Scanner;public class AOJ0009_Prime_Number {/** * @param args */static int prime[] = new int[1000000];public static void main(String[] args) {// TODO Auto-generated method stubgetans();Scanner cin = new Scanner(System.in);while(cin.hasNext()){int a = cin.nextInt();System.out.println(prime[a]);}}private static void getans() { //for(int i=0; i<1000000; i++)prime[i] = i; prime[1] = 0; prime[2] = 1; for(int i=2; i<1000000; i++) { if(prime[i] == -1) { prime[i] = prime[i-1];continue; } prime[i] = prime[i-1] + 1; for(int j=i*2; j<1000000; j+=i) { prime[j] = -1; } }}}