# 函数的嵌套调用：在一个函数内部调用另一个函数
def fn1():
    pass
def fn2():
    fn1()  # 函数的嵌套调用
def fn3():
    fn2()  # 函数的嵌套调用
fn3()

# 案例：
# 求两个数最大值
def max_two(n1, n2):
    if n1 > n2:
        return n1
    return n2

# 求三个数最大值
def max_three(n1, n2, n3):
    max = max_two(n1, n2)
    return max_two(max, n3)

# 求四个数最大值
def max_four(n1, n2, n3, n4):
    max = max_three(n1, n2, n3)
    return max_two(max, n4)
print(max_four(20, 50, 30, 50))