program ciur;
var f,g:text;
i,j,k,n,t:longint;
begin
assign(f,'ciur.in');reset(f);
assign(g,'ciur.out');rewrite(g);
read(f,n);
for i:=n downto 3 do
if i mod 2<>0 then begin
k:=0;
for j:=2 to i div 2 do
if i mod j=0 then begin break; k:=k+1;end;
if k=0 then t:=t+1;
end;
write(g,t+1);
close(f);
close(g);
end.