program ciur;
var f,g:text;
v:array[3..2000000] of boolean;
rez,n,i,j:longint;
begin
assign(f,'ciur.in');reset(f);
assign(g,'ciur.out');
rewrite(g);
readln(f,n);
rez:=1;
i:=3;
while i<=n do begin
if not(v[i]) then begin
inc(rez);
j:=i;
while j<=n div i do begin
v[i*j]:=true;
inc(j);
end;
end;
i:=i+2;
end;
writeln(g,rez);
close(f);
close(g);
end.