var a:array[1..10000001] of 0..1;
    i,n,j,nr:longint;
    k:int64;
begin
assign(input,'ciur.in');reset(input);
assign(output,'ciur.out');rewrite(output);
readln(n);
nr:=1;
i:=1;
for i:=1 to trunc(sqrt(n)) div 2 do
if a[i shl 1+1]=0 then
begin
inc(nr);
k:=(i shl 1+1)*(i shl 1+1);
for j:=1 to n div k do
a[j*k shr 1]:=1;
end;
write(nr);
end.