program fractii;
type
tabel=array [0..1000001] of integer;
var
t:tabel;
l:int64;
i:longint;
n,m,j,k:int64;
f1,f2:text;
begin
assign (f1,'fractii.in');
assign (f2,'fractii.out');
reset (f1);
rewrite (f2);
readln (f1,n);
l:=0;
for i:=1 to n do t[i]:=i;
for i:=2 to n do
if t[i]=i then begin
j:=0;
repeat
j:=j+i;
t[j]:=t[j]*(i-1) div i;
until j>=n;
end;
for i:=2 to n do
l:=l+t[i];
writeln (f2,2*l+1);
close (f1);
close (f2);
end.