type vec=array[1..1000000] of byte;
var i,j,k,nr,n,k1:int64;
    p:vec;
begin
assign(input,'fractii.in');
assign(output,'fractii.out');
reset(input);
rewrite(output);

read(n);

k:=n-1; {numarul fractiilor reductibile de forma 2/2 3/3...}
i:=2;
while i<(n div 2) do
      begin
      k1:=0;
      if p[i]=0 then
                begin
                j:=i+i;
                while j<=n do
                      begin
                      k:=k+2;
                      p[j]:=1;
                      j:=j+i;
                      inc(k1);
                      end;
                end;
      if k1<>0 then k:=k+(k1*(k1+1) div 2);
      inc(i);
      end;
nr:=n*n-k; {din numarul fractiilor existente scadem fractiile reductibile}
write(nr);

close(input);
close(output);

end.