---

# 定義羅馬數字和阿拉伯數字之間的對應關係

roman_to_int_map = {

    'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000

}

 

# 將羅馬數字轉換成阿拉伯數字

def roman_to_int(roman):

    total = 0

    prev_value = 0

    for char in reversed(roman):

        value = roman_to_int_map[char]

        if value < prev_value:

            total -= value

        else:

            total += value

        prev_value = value

    return total

 

# 將阿拉伯數字轉換成羅馬數字

def int_to_roman(num):

    int_to_roman_map = [

        (1000, 'M'), (900, 'CM'), (500, 'D'), (400, 'CD'),

        (100, 'C'), (90, 'XC'), (50, 'L'), (40, 'XL'),

        (10, 'X'), (9, 'IX'), (5, 'V'), (4, 'IV'), (1, 'I')

    ]

    result = ""

    for value, symbol in int_to_roman_map:

        while num >= value:

            result += symbol

            num -= value

    return result

 

# 處理每行測試資料，輸出兩個數字差的絕對值並轉換成羅馬數字

def process_lines():

    results = []

    while True:

        line = input().strip()

        if line == "#":

            break

        num1_roman, num2_roman = line.split()

        num1 = roman_to_int(num1_roman)

        num2 = roman_to_int(num2_roman)

        diff = abs(num1 - num2)

        if diff == 0:

            results.append("ZERO")

        else:

            results.append(int_to_roman(diff))

    

    # 輸出結果

    for result in results:

        print(result)

 

# 執行處理函數

process_lines()