#include <fstream>

using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

bool C[2000001];

void Ciur()
{
    for( int i = 2; i <= 1415; ++i )
    {
        if( !C[i] )
            for( int j = i + i; j <= 2000000; j += i )
                C[j] = 1;
    }
}

int main()
{
    C[0] = C[1] = 1;
    int N; fin >> N;
    Ciur();
    int nr = 0;
    for( int i = 1; i <= N; ++i )
        if( !C[i] )
            nr++;

    fout << nr;

    return 0;
}