#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;  
}