#include <iostream.h>
#include <fstream.h>

fstream in("fractii.in",ios::in),out("fractii.out",ios::out);

int n,i,j,TOTEM[1000001],NOTPRIM[1000001]; long long solutie;

int main()
{in>>n;

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

for(i=2;i<=n;++i)
{
if(NOTPRIM[i]==0) for(j=i;j<=n;j+=i)
		  {NOTPRIM[j]=1; TOTEM[j]/=i; TOTEM[j]*=i-1;}
solutie+=TOTEM[i];}

out<<1+(solutie << 1);}