const
 nmax=1000000;
var
 f:array[1..nmax] of longint;
 n,i,j,s:longint;
begin
 assign(input,'fractii.in');reset(input);
 readln(n);
 close(input);
 s:=0;
 for i:=2 to n do begin
  if f[i]=0 then
   for j:=2 to n div i do begin
    dec(f[i*j],i-1);
    dec(s,i-1);
   end;
 end;
 assign(output,'fractii.out');rewrite(output);
 write( n*n-n+2*s+1);
 close(output);
end.