var v,a,b,phi:array[1..1001001]of longint;
    n,l:longint;
    r:int64;
    i,j:longint;
begin
assign(input,'fractii.in'); reset(input);
assign(output,'fractii.out'); rewrite(output);
readln(n);r:=0;i:=0;j:=0; l:=trunc(sqrt(n));
for i:=2 to l do
if v[i]=0 then
for j:=1 to n div i do v[i*j]:=i;
for i:=l+1 to n do
if v[i]=0 then v[i]:=i;
for i:=2 to n do begin
a[i]:=v[i];
j:=i div a[i];
while j mod a[i]=0 do a[i]:=a[i]*v[i];
b[i]:=i div a[i];
if b[i]=1 then phi[i]:=i-i div v[i]
else
phi[i]:=phi[a[i]]*phi[b[i]];
end;
for i:=2 to n do r:=r+phi[i];
r:=2*r+1;
write(r);
close(input); close(output);
end.