bool isLeap(int year) {
  return (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0);
}

succ = lambda n: lambda f: lambda x: f (n (f) (x))
add = lambda a: lambda b: lambda f: lambda x: a (f) (b (f) (x))
zero = lambda f: lambda x: x
one = succ(zero)
two = succ(one)
three = succ(two)
four = succ(three)
five = succ(four)
nine = add(four)(five)
fst = lambda a: lambda b: a
snd = lambda a: lambda b: b
pair = lambda a: lambda b: lambda f: f (a) (b)
zadd = lambda a: lambda b: pair (add (a (fst)) (b (fst))) (add (a (snd)) (b (snd)))
phi = lambda p: pair (p (snd)) (succ (p (snd)))
pred = lambda n: n (phi) (z0) (fst)
sub = lambda a: lambda b: b (pred) (a)
true = lambda p: lambda q: p
false = lambda p: lambda q: q
and_ = lambda p: lambda q: p (q) (false)
or_ = lambda p: lambda q: p (true) (q)
zerop = lambda n: n (lambda x: false) (true)
leq = lambda a: lambda b: zerop (sub (a) (b))
eq = lambda a: lambda b: and_ (leq (a) (b)) (leq (b) (a))
zzerop = lambda n: eq (n (fst)) (n (snd))
zneg = lambda n: pair (n (snd)) (n (fst))
equal = lambda a: lambda b: zzerop (zadd (a) (zneg (b)))
z0 = pair(zero)(zero)
z3 = pair(three)(zero)
z4 = pair(four)(zero)
z5 = pair(five)(zero)
z9 = zadd(z4)(z5)
z_2 = pair(zero)(two)
sum = zadd
bool = lambda p: p (True) (False)