#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int e[1000001];
int main()
{
    long long unsigned s=1;
    int n,i,j;
    f>>n;
    for(i=2;i<=n;i++)
        e[i]=i;
    for(i=2;i<=n;i++)
    if(e[i]==i)
    for(j=i;j<=n;j+=i)
        e[j]=e[j]/i*(i-1);
    for(i=2;i<=n;i++)
    s+=2*e[i];
    g<<s;
    return 0;
}