#pragma region
#include <bits/stdc++.h>
using namespace std;
//#define ll long long

const long N = 2'000'005;
bool ciur[N];
#pragma endregion

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

    long n; scanf("%ld", &n);

    ciur[0] = ciur[1] = true;
    int cnt = 0;
    for (long i = 2; i <= n; i++) {
        if (i <= n && ciur[i] == false)
            ++cnt;
        for (long j = 2; i * j <= n; j++)
            ciur[i * j] = true;
    }

    printf("%d", cnt);

    fclose(stdin);
    fclose(stdout);
    return 0;
}