#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int ciur[1000005],n,i,j;
long long int cnt=0;
int main()
{
    in>>n;
    for(i=2;i<=n;i++)
    ciur[i]=i-1;
    for(i=2;i<=n;i++)
    {
        for(j=2*i;j<=n;j+=i)
        ciur[j]-=ciur[i];
        cnt+=ciur[i]*2;
    }
    out<<cnt+1;
    return 0;
}