var i,s,a:longint;
begin
read(a);
for i:=1900 to a do
if ((i mod 4=0)and(i mod 100<>0))or(i mod 400=0) then inc(s);
write(s);
end.
/**************************************************************
	Problem: 1749
	User: admin
	Language: Pascal
	Result: Wrong Answer
****************************************************************/