program ciur;
var v:array[2..2000000]of boolean;i,j,k,n:longint;
    f,g:text;
 begin
    assign(f,'ciur.in'); reset(f);
    assign(g,'ciur.out');rewrite(g);
     readln(f,n);
     for i:=2 to n do
      if not v[i] then
       begin k:=k+1;
     for j:=2 to n div i do
       v[i*j]:=true;
       end;
      write(g,k);
     close(f);close(g);
      end.