#include <fstream>

using namespace std;
ifstream cin("ciur.in");
ofstream cout("ciur.out");

int main()
{
    int N, i, j, rez = 0;
    bool v[2000000] = {0};
    cin>>N;
    for(i = 2; i*i <= N; i++)
        {
            if(!v[i])
            {
                for(j = i*i; j <= N; j+=i)
                {
                    v[j] = true;
                }
            }
        }
    for(i = 1; i <=N; i++)
        rez+=v[i];
    cout<<N-rez-1;
}