coke.py

def main():
    amtDue = 50
    validCoins = [5,10,25]
    while (amtDue>0):
        print(f'Amount Due: {amtDue}')
        coin = int(input('Insert Coin: '))
        if coin not in validCoins:
            continue
        else:
            amtDue = amtDue - coin
    changeOwed = -amtDue
    print(f'Change Owed: {changeOwed}')

main()