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

int main(){
	int n, temp, counter;
	temp = 0;
	counter= 0;
	while(cin >> n){
		vector<int> num(n);
		num[0], num[1] = 1;
		for(int i = 0; i < n; i++){
			if(num[i] == 0){
				for(int j = 0; temp < n; j++){
					temp = i * j;
					num[temp] = 1;
					counter++;
				}
			}
		}
		cout << counter << endl;
	}
	return(0);
}