#include<fstream>
#define MAXN 1000000
using namespace std;
ofstream fout("ciur.out");
ifstream fin("ciur.in");

int main()
{
    int A[MAXN]={0},N,i,j,prime = 1;
    fin >> N;
    for(i = 1; 2*i+1 <= N; i++){
        if(!A[i]){
            prime++;
            for(j = 3*i + 1; j <= N; j+=2*i+1){
                A[j] = 1;
            }
        }
    }
    fout << prime;
    fin.close();
    fout.close();
    return 0;
}