#include <fstream>

using namespace std;

int a[1000001];

ifstream cin ("fractii.in");
ofstream cout ("fractii.out");

int main()
{
    int n;
    unsigned long long s=0;
    cin>>n;

    for(int i = 1;i<=n;++i)
        a[i]=i;

    for(int i = 2;i<=n;++i){
        if(a[i]==i){
            a[i]--;
            for(int j = 2;j*i<=n;j++)
                a[i*j]=a[i*j]/i*(i-1);
        }
    }

    for(int i = 2;i<=n;++i)
        s+=a[i];

    cout<<2*s+1;

    return 0;
}