MIT 6.0001 ps1 a

# House Hunting

# total_cost: the cost of your dream home
# portion_down_payment: 预付款 assume 0.25
# current_savings: start with 0
# r: annual return of investment current_savings*r/12
# annual_salary
# portion_saved: decimal form e.g.0.1
# At the end of each month,
# your savings will be increased by the return on your investment, 
# plus a percentage of your monthly salary

# input:
# annual_salary
# portion_saved
# total_cost

# output:
# months

import math
annual_salary = int(input('Enter your annual salary:'))
portion_salary = float(input('Enter the percent of your salary to save, as a decimal:'))
total_cost = int(input('Enter the cost of your dream home:'))

portion_down_payment = 0.25 * total_cost
month = 1
r = 0.04
portion_saved = portion_salary * annual_salary / 12
current_savings = portion_saved

while current_savings < portion_down_payment:
    current_savings = current_savings * r / 12 + portion_saved + current_savings
    month += 1
    
print('Number of months: ', math.ceil(month))