#include<iostream>
using namespace std;

bool IsPrime(int n){

    if(n % 2 == 0)
        return false;
 
    for(int i = 3; i * i <= n; i += 2)
         if(n % i == 0)
            return false;
    return true;
}
int CheckNum(int input){
	int count = 1;

	for(int i = 2; i < input; ++i){

		if(IsPrime(i)) ++count;
	}
	return count;
}
int main() {
	int input;

	cout << CheckNum(input) << endl;
}