#include <fstream>
using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");
#define int long long
int v[1000000];

signed main()
{
    int i,n,sum=0,j;cin>>n;
    for(i=1;i<=n;i++) v[i]=i;
    for(i=2;i<=n;i++){
        if(v[i]==i){
            v[i]--;
            for(j=2*i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
        }
        sum+=v[i];
    }
    cout<<2*sum+1;
    return 0;
}