#include<iostream>
#include<fstream>
#include<algorithm>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int i,j,v[1000010],n,ok;
long long s;

int main()
{
    fin>>n;
    for(i=2;i<=n;i++)
        if(v[i]==0)
        {
            ok=n/i-1;
            for(j=i;j<=n;j+=i)
                v[j]+=ok;
        }
    s=n*n*1LL;
    for(i=2;i<=n;i++)
    {
        s-=v[i];
        s-=1;
    }
    fout<<s;
    fin.close();
    fout.close();
    return 0;
}