program fractii;
var f:text;
    nr,d,c,i,j,n:longint;
    ok:boolean;
    t:array[1..10000] of longint;
begin
assign(f,'fractii.in'); reset(f);
readln(f,n);
close(f);
for i:=2 to n do
begin
     d:=2;  ok:=true;
     while  (ok) and (d<= trunc(sqrt(i))) do
          if i mod d=0 then ok:=false
                       else d:=d+1;
    if ok then t[i]:=(i-1)
          else begin
                    j:= i div d;
                    if j mod d= 0 then c:=(i-1) div j
                                  else c:=0;
                    t[i]:=(i-1)-((i-1) div d)-((i-1) div j)+c;
                end;
end;
nr:=1;
for i:= 2 to n do
nr:=nr+2*t[i];
assign(f,'fractii.out'); rewrite(f);
writeln(f,nr);
close(f);
end.