var a:array[1..1000000]of int64; s:int64;  i,n,j:longint; f:text;
begin
assign(f,'fractii.in');reset(f);
read(f,n);
s:=1;a[2]:=1; assign(f,'fractii.out'); rewrite(f);
for i:=2 to n do begin
                     if a[i]=0 then a[i]:=i-1;
                     s:=s+2*a[i];
                     if i<(n div 2)+1 then begin j:=2*i;
                     while j<=n do begin
                                        if a[j]=0 then a[j]:=j-1-a[i]
                                                  else a[j]:=a[j]-a[i];
                                        j:=j+i
                                   end; end;
                 end;
writeln(f,s); close(f);
end.