#include <fstream>
#include <iostream>
#include <vector>
using namespace std;

ifstream f("fractii.in");
ofstream o("fractii.out");

main()
{
    int n,s=0;
    long long k,m;
    f>>n;
    vector<bool>t(n*n);
    for (long long i=0;i<n*n;i++)
    {
        t[i]=true;
    }
    for (long long i=1;i<=n*n;i++)
    {
        if(t[i-1])
        {
            s++;
            k=2*i+n;
            if(n>i){m=n/i;} else {m=i/n;}
            for (long long j=0;j<m-1;j++)
            {
                t[k-1]=false;
                k=k+i+n;
            }
        }
    }
    o<<s;
}