#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int phi[2000001],n;
long long cnt;
int main()
{
    cin>>n;
	for(int i=1;i<=n;++i)
        phi[i]=i-1;
    for(int i=2;i<=n;++i)
        for(int j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    for(int i=2;i<=n;i++)
        cnt+=phi[i];
    cnt=2*cnt+1;
    cout<<cnt;

}