Program Ciur;
var A:array[1..2000000] of boolean;
n,i,j,s:0..2000000;
f,g: text;
begin
assign(f,'ciur.in');
assign(g,'ciur.out');
reset(f);
rewrite(g);
readln(f,n);
i:= 2;
while i<=n do begin
if A[i] = false then begin 
 j:=0;
 while (sqr(i) + i*j <= n) do begin
  A[sqr(i) + i*j]:= true;
  j:= j + 1;
  end;
 s:=s+1;
 end;
i:= i+1;
end;
writeln(g,s);
close(f);
close(g);
end.