program fractii;
type s1=array [1..1000000] of real;
     s2=array [1..1000000] of integer;
var f,g:text;
    d,suma,n,cop,p:integer;
    i,j:longint;
    a:s1;
    t:s2;
begin 
assign(f,'fractii.in');reset(f);
assign(g,'fractii.out');rewrite(g);

read(f,n);

for i:=2 to n do
 if a[i]=0 then
  for j:=2 to (n div i) do
        a[i*j]:=1;
suma:=1;
for i:=1 to n do
    begin
    if a[i]=0 then t[i]:=i-1
              else
    begin
    d:=2;
    while i mod d<>0 do
          inc(d);
    p:=1;
    cop:=i;
    while cop mod d=0 do
          begin
          cop:=cop div d;
          p:=p*d;
          end;
    if cop=1 then t[i]:=i-(i div d)
             else t[i]:=t[p]*t[cop];
    end;
    suma:=suma+t[i];
    end;
write(g,2*suma-1);
close(f);
close(g);
end.