#include<iostream>
#include<string>
using namespace std;

int main(){
	int num;
	int count = 0;
	int i,j;

	cout << "数字を入力してください" << endl << "number :";
	cin >> num;

	for(i=2; i<num; i++){
		for(j=2; j<i; j++){
			if(i%j ==0){
				break;
			}
		}
		if(j == i){
			count++;
		}
	}
	cout << count << endl;
	cin >> num;
	return 0;
}