#include<fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int a[1000000];
void read_number(long long& n)
{
    f>>n;
}
void calculate_how_many(long long n)
{
    long long nb=n*n;
    int i,j,counter=0,numbers=0;
    for(i=1;i<=n;i++)
        a[i]=1;
    for(i=2;i<=n;i++)
        if(a[i]==1)
        {
            counter=0;
            numbers=1;
            for(j=i+i;j<=n;j+=i)
            {
                numbers++;
                if(a[j]==1)
                {
                   counter++;
                   a[j]=0;
                }
            }
            nb-=counter*(numbers-counter)*2+counter*(counter-1)+(numbers-1-counter)*2;
        }
    nb-=n-1;
    g<<nb<<"\n";
}
int main()
{
    long long n;
    read_number(n);
    calculate_how_many(n);
}