var n,nr,j,i,k:longint;
    a:array[2..2000000]of byte;
    f,g:text;
begin
assign(f,'ciur.in');
reset(f);
read(f,n);nr:=0;
for i:=2 to n do a[i]:=0;
for i:=2 to n do
     if a[i]<>1 then
          begin
          k:=0;
          inc(nr);
          j:=i;
           repeat
           inc(j,i);
           if j>n then k:=1
           else a[j]:=1;
           until (j>n)or(k=1);
          end;
close(f);
assign(g,'ciur.out');
rewrite(g);
writeln(g,nr);
close(g);
end.