program fractr;
var a:array[1..1000000] of longint;
    n,i,j:longint;
    s:qword;
begin
assign(input,'fractii.in'); reset(input);
assign(output,'fractii.out'); rewrite(output);
read(n);
close(input);
for i:=2 to n do a[i]:=i;
s:=2;
for i:=2 to n do begin
        if a[i]=i then begin
                j:=i;
                while j<=n do begin
                              a[j]:=a[j] div i;
                              a[j]:=a[j]*(i-1);
                              j:=j+i;
                              end;
                       end;
                s:=s+2*a[i];
                end;
s:=s-1;
write(s);
close(output);
end.