var f,g:text;
    n,i,k,j:longint;
begin assign(f,'fractii.in'); reset(f); assign(g,'fractii.out'); rewrite(g);
read(f,n); k:=n;                            j:=1;
for i:=2 to n do begin   k:=k+1; if i mod 2=0 then begin while j<=n do begin if(i mod j<>0) and (j mod i<>0) then k:=k+1;j:=j+2; end; end
else
for j:=1 to n do if(i mod j<>0) and (j mod i<>0) then k:=k+1;
end;
write(g,k);
close(g);
end.