#include <fstream>
#define NMAX 1000000
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int phi[NMAX+3];

int main()
{
    long long n,cnt=0,i,j;
    in>>n;
    for(int i=1;i<=n;i++)
        phi[i]=i-1;
    for(i=2;i<=n;i++)
        {for(j=i*2;j<=n;j+=i)
            phi[j]-=phi[i];
            cnt+=phi[i]*2;}

    out<<cnt+1;
    return 0;
}