#include <fstream>
#include <iostream>
using namespace std;

int n, fractii, v[1000001];

int cmmdc(int a, int b) {
    int ca = a;
    int cb = b;
    int c;
    while(cb) {
      c = ca % cb;
      ca = cb;
      cb = c;
    }
    return ca;
}


int main() {
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f >> n;
    v[0] = 1;
    v[1] = 1;
    fractii = n * (n-1) + 1;
   // for(int i = 1; i <= n; i++)
       // for(int j = 1; j <= n; j++)
          //  if(cmmdc(i, j) == 1)
          //      fractii++;

    for(int i = 2; i <= n; i++)
        if(!v[i]) {
            int m = 0;
            for(int j = 2; j*i <= n; j++) {
                v[i*j] = 1;
                m++;
                //cout << i << '/' << i*j << endl;
            }
            //cout << m << ' '<< i << endl;
            fractii -= (m+1)*m;
        }

    g << fractii;
    f.close();
    g.close();
    return 0;
}