var t:array[1..2000005] of integer;
    n,i,j,x:longint;
begin
assign(input,'ciur.in'); reset(input);
assign(output.'ciur.in'); rewrite(output);
readln(n); t[1]:=1; x:=1;
for i:=2 to trunc(sqrt(n)) do
 if t[i]=0 then
  for j:=2 to n div i do
   if t[i*j]=0 then
    begin
     t[i*j]:=1;
     inc(x)
    end;
writeln(n-x);
close(input);
close(output)
end.