program pascal;
var i,j,x:integer;
    n:longint;
    v:array[2..1000] of boolean;
    p,q:text;
begin
assign(p,'ciur.in');
reset(p);
assign(q,'ciur.out');
rewrite(q);
read(p,n);
for i:=2 to n do begin
                 if v[i]=false then begin
                                    j:=i+i;
                                    while j<= n do begin
                                                   v[j]:=true;
                                                   j:=j+1;
                                                   end;
end;
end;
x:=0;
for i:=2 to n do if v[i]=false then x:=x+1;
write(q,x);
close(p);
close(q);
end.