#include <fstream>
 
#define MAX 1000001
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
 
int main(){
    long long answer=0,ciur[MAX],i,j,n;
    f >> n;
 
    for (i = 1; i <= n; i++)
        ciur[i] = i;
 
    for (i = 2; i <= n; i++){
        if (ciur[i] == i){
                for (j = i; j <= n; j += i){
                ciur[j] =(ciur[j] / i)*(i - 1);
            }
        }
    }
    for (i = 2; i <= n; i++){
        answer += ciur[i];
 
    }
    g << 2*answer+1;
 
    return 0;
}