#include<stdio.h>

long int N,i,p,k,j,biggie[1000002],div[7],ratio=1;
long long int S;
float tot;




int main()

{

freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%ld",&N);
for(k=1;k<=N;k++)
 {
  biggie[k]=k;
 }
for(i=2;i<=N;i++)
 {
  if(biggie[i]==i)
  {
   for(j=1;i*j<=N;j++)
    biggie[i*j]*=(float)(i-1)/i;
  }
 }
for(i=1;i<=N;i++)
 S+=biggie[i];

printf("%lld",S*2-1);



fcloseall();
return 0;
}