#include <fstream>
#define dim 1000005
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n,i,f[dim],j;
long long s;
int main(){
    fin>>n;
    for(i=2;i<=n;i++){
        f[i]=i;
    }
    for(i=2;i<=n;i++){
        if(f[i]==i){
            for(j=i;j<=n;j+=i){
                f[j]=f[j]/i*(i-1);
            }
        }
    }

    for(i=1;i<=n;i++){
        s+=(f[i]*2);
    }
    fout<<s+1<<"\n";

    return 0;
}