#-*-coding=gbk-*-

import sys

import random

a=[]

try:

    for x in range(1,20+1,1): #打印20人数编号

        a.append(x)

    i=0

    key=raw_input("请输入a，开始抽奖号码:")

    while (key=="a"):

        b=random.choice (a)

        #b=str(b)

        i+=1

        print "     第%d个中奖号: %s"% (int(i),b)

        a.remove(b)

        key2=raw_input("请输入a，开始抽奖号码:")

    else:

        print ('ERROR!!')

except IndexError as e:

    print "已经抽完！"