#include<stdio.h>

int  n,i,j;
long long phi[1000111],sol;

int main(){

FILE *f=fopen("fractii.in","r");
fscanf(f,"%d",&n);
fclose(f);

  for(i=2;i<=n;i++)
  phi[i]=i-1;

  for(i=2;i<=n;i++)
    for(j=i+i;j<=n;j+=i)
    phi[j]-=phi[i];

    
  for(i=2;i<=n;i++)
  sol+=phi[i];

  sol+=sol;sol++;

FILE *g=fopen("fractii.out","w");
fprintf(f,"%lld",sol);
fclose(g);

return 0;
}