## ps1, prob 3
print 'Given a starting balance and interest rate, this program will calculate your minimum monthly payment,'
print 'that will pay off your balance in 12 months or less.'

balance = float(raw_input('Enter the outstanding balance on your credit card:'))
interestrate = float(raw_input('Enter the annual credit card interest rate as a decimal:'))

lowerbound=balance/12
upperbound=(balance*(1+(interestrate/12))**12)/12
payment=(lowerbound+upperbound)/2

def twelvemonth ():
    global payment
    global lowerbound
    global upperbound
    month = 0

    while month <=11:
        month = month + 1
        if month==1:
            calcbalance = balance
        intowed = calcbalance*(interestrate/12)
        calcbalance = calcbalance + intowed - payment
        if -.12 <= calcbalance <= 0 and month == 12:
            print 'Monthly payment to pay off debt in 1 year: $' + str(round(payment, 2))
            print 'Number of months needed:  ' + str(month)
            print 'Balance:  $' + str(round(calcbalance, 2))
        if calcbalance < -.12 and month == 12:
            upperbound=payment
            payment=(payment+lowerbound)/2
            twelvemonth ()
        if calcbalance > 0 and month == 12:
            lowerbound=payment
            payment=(payment+upperbound)/2
            twelvemonth ()

twelvemonth ()