code7

import java.util.Scanner;
public class code7 {

//判断数是不是素数
public static boolean number(int num) {		
	for (int i = 2; i <= Math.sqrt(num); i++) {
		if (num % i == 0) {
			return false;
		}
	}
	return true;
}

//判断相邻素数之间的值是不是2
public static void judge(int num) {
	
	//存放素数
	int[] list2 = new int[num];
	int counter = 0;
	for (int i = 1; i < num; i++) {
		if (number(i)) {
			list2[counter++] = i;
		}
	}
	
	//遍历list2 相差1的相邻素数+1
	int count = 0;
	for (int i = 1; i < list2.length; i++) {
		if (list2[i] - list2[i - 1] == 2) {
			count++;
		}
	}
	System.out.println(count);
}

public static void main(String[] args) {
	// TODO Auto-generated method stub
	Scanner in = new Scanner(System.in);
	int x = in.nextInt();
	if (x > 100000 || x <= 3) {
		System.out.println("no");
	}
	judge(x);	
}

}