---
title: a013
tags: Python3.6.2
---

import sys
dic = {
    'M' : 1000,
    'CM' : 900,
    'D' : 500,
    'CD' : 400,
    'C' : 100,
    'XC' : 90,
    'L' : 50,
    'XL' : 40,
    'X' : 10,
    'IX' : 9,
    'V' : 5,
    'IV' : 4,
    'I' : 1
}

def conversion(text):
    num_list = []
    for s in text:
        num_list.append(dic[s])
    for i, v in enumerate(num_list[:len(num_list)-1]):
        if num_list[i] < num_list[i+1]:
            num_list.pop(i)
            num_list.insert(i, -v)
    return sum(num_list)

def process_output(num):
    output = ''
    for k, v in dic.items():
        while num - v >= 0:
            output += k
            num    -= v
    return output

for s in sys.stdin:
    if '#' in s:
        break
    str_split = s.replace('\r', '').replace('\n', '').split(' ')
    value = abs(conversion(str_split[0]) - conversion(str_split[1]))
    if value == 0:
        print('ZERO')
    else:
        print(process_output(value))