#include<fstream>   
using namespace std;   
int prim[]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,   
89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,   
193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,   
307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,   
421,431,433,439,443,449,457,461,463,467,479,487,491,499,   
503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,   
631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,   
757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,   
881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009};   
int phi[1000001], n;   
int main(){   
  int i, j;   
  ifstream f("fractii.in");   
  f>>n;   
  f.close();   
  phi[1]=1;   
  phi[2]=1;   
  phi[3]=2;   
  phi[4]=2;   
  phi[5]=4;   
  for(i=6;i<=n;i++){   
    for(j=0;(prim[j]*prim[j]<=i)&&i%prim[j]!=0;j++);   
    if(prim[j]*prim[j]>i)   
      phi[i]=i-1;   
    else{   
      int cat=prim[j]-1;   
      int nr=i/prim[j];   
      while(nr%prim[j]==0){   
    nr/=prim[j];   
    cat*=prim[j];   
      }   
      phi[i]=phi[nr]*cat;   
    }   
  }   
  long long suma=0;   
  for(i=2;i<=n;i++)   
    suma+=phi[i];   
  suma<<=1;   
  ++suma;   
  ofstream g("fractii.out");   
  g<<suma<<'\n';   
  g.close();   
  return 0;   
}