python，看看这题，遇到问题了

怎么改，让它输出次数21

a=100
year =0
while a>0:
    a=a*1.08-10
    year+=1
print(year)

#!/usr/bin/python
# -*- coding: UTF-8 -*-
"""
@author: Roc-xb
"""

if __name__ == '__main__':
    money = 100
    year = 0
    while money > 0:
        money = money * 1.08 - 10
        year += 1
    print(year)