#include <cstdio>
#include <cmath>

using namespace std;

bool prime[2000005];

// 1 - daca nu este prim
// 0 - daca este prim

int main() {
	freopen("ciur.in", "r", stdin);
	freopen("ciur.out", "w", stdout);

	int N;

	scanf("%d", &N);

	int SQRT = sqrt(N);

	prime[1] = 1;
	int counter = N;
	
	for (int i = 2;i <= SQRT;i ++) {
		for (int j = i + i;j <= N;j += i) {
			prime[j] = 1;
			counter --;
		}
	}



	printf("%d", counter);
	return 0;
}