public class PrimeCounter {
    // Returns true if x is prime, and false otherwise.
    private static boolean isPrime(int x) {
       for (int i = 2; i <= x / 2; i++) {
           if (x % i == 0) {
               return false;
           }
        }
        return true;
    }

    // Returns the number of primes <= N.
    private static int primes(int N) {
       int counter = 1;
       for (int num = 2; counter <= N; num++) {
       if (isPrime(N)) {
           counter++;
        }
       }
        return counter;
    }

    // Entry point. [DO NOT EDIT]
    public static void main(String[] args) {
        int N = Integer.parseInt(args[0]);
        System.out.println(primes(N));
    }
}