#include <iostream>
#include <fstream>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
const int NMAX=1<<17;
unsigned char v[NMAX];
int main()
{
    int n, i, j, i2, nrprime = 0;
    f>>n;
    for(i=3;i<=n;i+=2)
    {if (v[i>>4]&(1<<((i>>1)&7)))continue;
    nrprime++;
        for(j=3*i;j<=n;j+=i<<1)
        v[j>>4]|=1<<((j>>1)&7);
    }
    g<<nrprime+1;

    return 0;
}