#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
const int VMAX=500001;
long long C[VMAX],N;
void CIUR(long long &nr)
{
    for(long long d=3;d<=N/2;d+=2)
        if(C[d]==0)
        {
            long long cnt=1;
            for(long long m=d*2;m<=N;m+=d)
            {
                if(m%2==1)
                    C[m]=1;
                cnt++;
            }
            nr=nr-cnt*(cnt-1);
        }
}

int main()
{
    fin>>N;
    long long nr=N*N-(N-1)-(N/2)*(N/2-1);
    CIUR(nr);
    fout<<nr<<'\n';

    return 0;
}