program ciur;
var v:array[1..1000000] of longint;
    i,j,n,c:longint;
 begin
  readln(n);
  for i:=1 to n do
   v[i]:=0;
  for i:=2 to n div 2 do
   for j:=2 to n div i do
    v[i*j]:=1;
  for i:=2 to n do
   if v[i]=0 then
    c:=c+1;
  writeln(C);
   readln;
  end.