program suma;   
const fin = 'fractii.in';   
      fout = 'fractii.out';   
var c,i,j,n:longint;   
    sol:int64;   
    t:array [1..1000000] of longint;   
begin  
  {citire}  
  assign(input,fin);   
  assign(output,fout);   
  reset(input);   
  rewrite(output);   
  read(n);   
  for i:=1 to n do  
    t[i]:=i-1;   
  for i:= 2 to n do  
  begin  
    j:=2*i;   
    while j<=n do  
    begin  
      dec(t[j],t[i]);   
      inc(j,i);   
    end;   
  end;   
  sol:=1;   
  for i:=2 to n do  
    sol:=sol+2*t[i];   
  {tipar}  
  write(sol);   
  close(input);   
  close(output);   
end.