program PbFractii2;

var f,g:text; n,i,j,nr:longint;  a:array[1..1000000]of longint;  nr:int64;
begin
assign(f,'fractii.in');reset(f);
assign(g,'fractii.out');rewrite(g);
read(f,n);

nr:=1;
for i:=2 to n do
 a[i]:=i-1;
for i:2 to n do
 begin
 nr:=nr+2*a[i];
 h:=n div i;
 for j:=2 to h do a[i*j]:=a[i*j]-a[i];
 end;
writeln(nr);
close(f);
close(g);
end.