var n,i,k,j:longint;
    v:array[2..10000] of boolean;
    f,g:text;
begin
assign(f,'ciur.in');reset(f);
readln(f,n);close(f);
assign(g,'ciur.out');rewrite(g);
if n=2 then writeln(g,1)
       else begin
for i:=2 to n do v[i]:=true;
k:=0;
for i:=2 to n-1 do
 if v[i] then begin k:=k+1;
   for j:=i+1 to n do if j mod i=0 then v[j]:=false;
              end;
writeln(g,k);
end;
close(g);
end.