var a:array[1..2,1..1000000]of int64; n,s,v,j:int64;  i:longint;f:text;
begin
assign(f,'fractii.in');reset(f);
read(f,n);
s:=1;a[1,2]:=1; assign(f,'fractii.out'); rewrite(f);
for i:=2 to n do begin if a[1,i]=0 then a[1,i]:=i-1; s:=s+2*a[1,i]; j:=2*i; v:=1; if a[2,i]=0 then while j<=n do begin if a[1,j]=0 then a[1,j]:=j-1-v else a[1,j]:=a[1,j]-v; a[2,j]:=1; v:=v+1; j:=j+i end; end;
writeln(f,s); close(f);
end.