#include <iostream>
using namespace std;

int arr[1000000];

void ar()
{
	int cnt;
	arr[2] = 1;
	int j;
	int i = 3;
	for (; i < 100000; ++i) {
		cnt = 1;
		for (j = 2; j < i; ++j) {
			if (i%j == 0) {
				arr[i] = arr[i - 1];
				--cnt;
				break;
			}
		}
		arr[i] = arr[i - 1] + cnt;
	}
}

int main()
{
	int x;
	ar();
	while (cin >> x) {
		cout << arr[x] << endl;
	}
	return 0;
}