// Coroana te rog
// Ciurul lui Eratostene
#include <iostream>
int main() {
size_t n, c = 0;
std::cin >> n;
bool *v = new bool[n + 1]();
for (size_t j, i = 2; i <= n; ++i)
for (j = i + i; j <= n; j += i)
if (!v[j]) {
++c;
v[j] = true;
}
std::cout << n - c;
delete[] v;
}
