#include <cstdio>
#include <bitset>
using namespace std;

bitset<1000010> e;

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

    int n;
    scanf("%d", &n);

    for (int i = 3; i * i < n; i += 2) {
        if (e[i >> 1]) {
            continue;
        }

        for (int j = i * i; j <= n; j += (i << 1)) {
            e[j >> 1] = true;
        }
    }

    int res = 1;
    for (int i = 3; i <= n; i += 2) {
        if (!e[i >> 1]) {
            ++res;
        }
    }

    printf("%d\n", res);

    return 0;
}