#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
const int DIM = 2e6;
int n, rez = 0;
bitset <DIM+10>ciur;

int main()
{
    ciur[0] = ciur[1] = 1;
    for(int i=3; i<=1415; i+=2)
        if(!ciur[i])
            for(int j=i*i; j<=DIM; j+=i) ciur[j] = 1;
    fin >> n;
    for(int i=3; i<=n; i+=2) rez += !ciur[i];
    fout << rez + 1; ///si cu 2

    return 0;
}