#include <fstream>
#include <bitset>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
bitset<2000003> bit;
int n,k;
int main() {
    in >> n;
    for(int i = 2; i <= n; i++)
        if(!bit[i])
            for(long long j = 1LL*i*i; j <= n; j += i)
                bit[j] = 1;
    out << n-bit.count()-1;
    return 0;
}