var i,j,n,nr:longint;
    phi:array[1..1000000] of longint;
    f,g:text;
begin
 assign(f,'fractii.in');
 assign(g,'fractii.out');
 reset(f);rewrite(g);
 read(f,n);
 nr:=1;
 for i:=1 to n do phi[i]:=i-1;
 for i:=2 to n do begin j:=i*2;
 while (j<=n) do begin
 phi[j]:=phi[j]-phi[i];
 j:=j+i;end;
 nr:=nr+2*phi[i];
 end;
 write(g,nr);
 close(f);close(g);
end.