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# "Do U know Y this works?"
 
U = lambda f: f(f)
 
Y = lambda f: lambda n: f(Y(f))(n)
 
@U
def fact(g):
        return lambda n: (n < 2) and 1 or n * g(g)(n - 1)
 
print(fact(5))
 
@Y
def fib(g):
        return lambda n: (n >= 2) and g(n - 1) + g(n - 2) or n
 
print(fib(6))