def conversion(num,m):    #进制转换,最多转换三十六进制吧
    baseChar = "0123456789abcdefghijklmnopqrstuvwxyz"
    tempNum = num
    if num==0:
        return 0
    result = []
    while tempNum>0:
        tempNum,b = divmod(tempNum,m)
        result.append(baseChar[b])
    return "".join(result[::-1])

while True:
    try:
        digitList = list(map(int,input().split()))
        if digitList[0]==0:
            break
        print(conversion(digitList[1]+digitList[2],digitList[0]))
    except Exception:
        break

python解法，简单易懂，写了个进制转换的函数。

def baseN(num, b):
    return ((num == 0) and "0") or (baseN(num // b, b).lstrip("0") + "0123456789abcdefghijklmnopqrstuvwxyz"[num % b])


while True:
    try:
        a = input()
        if a != "0":
            jinzhi, num1, num2 = map(int, a.split())
            print(baseN((num1 + num2), jinzhi))

    except:
        break