import sys
import random


class Machine:
    coins = {
        "1/2": 1/2,
        "1/4": 1/4,
        "1/8": 1/8,
        "1/10": 1/10
    }
    price = round(
        coins["1/%d" % random.choice([2, 4, 8, 10])] * random.randint(5, 10),
        3
    )
    state = 0

    def run(self):
        while self.state < self.price:
            print("".center(64, "-"))
            print("# Your balance:", self.state)
            print("# You need:", self.price)
            print("# Accepting coins:", ", ".join(self.coins.keys()))

            coin = self.expect_coin()
            self.state += coin
            if self.state >= self.price:
                print("\nOK:", self.state)
                if self.state > self.price:
                    print("You overpaid by: %.3f" % (self.state - self.price))
                return

    def expect_coin(self):
        coin = None
        while coin not in self.coins:
            try:
                coin = input("Insert coin> ")
                coin = coin.strip()
                if coin not in self.coins:
                    print("Unsupported coin:", coin)
            except KeyboardInterrupt as e:
                print("\nGoodbye. No change, sorry.")
                sys.exit(0)
            except:
                continue
        return self.coins[coin]


m = Machine()
m.run()