#求a+aa+aaa+aaaa+aaaaa和的三种算法

#两次递归调用
def num1(a,b):
    if b ==1:
        return a
    else:
        return 10 * num1(a,b-1) + a
def sum1(a,b):
    if b ==1:
        return a
    else:
        return sum1(a,b-1)+num1(a,b)
print(sum1(2,3))

#while循环计算
def sum2(a,b):
    n = a
    p = 1
    m = a
    while p < b:
        n = 10*n + a
        m += n
        p += 1
    return m

print(sum2(3,3))

#for循环计算
def sum3(a,b):
    n = a
    m = a
    for i in range(b-1):
        n = 10*n + a
        m += n
    return m
print(sum3(2,3))