var f,g:text;
    a:array[1..2000000]of 0..1;
    n,b:1..2000000;
function ciur(x:longint):longint;
var y,nr,i:longint;
begin  nr:=0;
for i:=2 to x do
   if a[i]=0 then begin  for y:=i+1 to x do
                            if y mod i =0 then a[y]:=1;
                         nr:=nr+1;
                  end;
ciur:=nr;
end;
begin
assign(f,'ciur.in'); reset(f); assign(g,'ciur.out'); rewrite(g);
read(f,n);
b:=ciur(n);
write(g,b);
close(f); close(g);
end.