using namespace std;



#define fisier "ciur"

#ifdef fisier
    #include <fstream>
    ifstream in(fisier ".in");
    ofstream out(fisier ".out");
#else
    #include <iostream>
    #define in cin
    #define out cout
#endif



bool v[2000001];
int n;



void build() {

    long long i, j, np2 = n/2, npi;

    for (i = 2; i <= np2; i++) {

        npi = n/i;

        for (j = 2; j <= npi; j++) {

            v[i * j] = true;

        }

    }

}



int main() {

    in >> n;

    build();

    int s = 0;
    for (int i = 2; i <= n; i++) {

        if (!v[i]) s++;

    }

    out << s;


}
















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