import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
    public static void main (String[] args) throws java.lang.Exception
    {
        //your code here
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        boolean[] arr = new boolean[n + 1];
        // initially all numbers are cube_free
        for(int i = 0; i<=n; i++)
            arr[i] = false;

        for(int i = 2; i * i * i<=n; i++) {
            arr[i * i * i] = true;
        }

        for(int i = 2; i<=n; i++) {
            if(arr[i]) {
                for(int j = 2; j * i <= n; j++) {
                    arr[i * j] = true;
                }
            }
        }

        if(arr[n]) {
            System.out.println(-1);
            return;
        }
        int cnt = 0;
        for(int i = 1; i<=n; i++) {
            if(!arr[i]) {
                cnt++;
            }
        }
        System.out.println(cnt);
    }
}