# ZeroJudge - a013: 羅馬數字
### 題目連結：https://zerojudge.tw/ShowProblem?problemid=a013
###### tags: `ZeroJudge` `模擬`

#include <iostream>
#include <string>
#include <cmath>
using namespace std;

int romanValue[7] = { 1, 5, 10, 50, 100, 500, 1000 }, combineValue[13] = { 1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000 };
string symbols = "IVXLCDM", combination[13] = { "I", "IV", "V", "IX", "X", "XL", "L", "XC", "C", "CD", "D", "CM", "M" };

int FindSymbol(char letter) {
	for (int i = 0; i < 7; ++i)
		if (symbols[i] == letter)
			return i;
	return -1;
}

int RomanToArabic(string roman) {
	int arabic = 0, previous = 0, nowValue;
	for (int i = roman.size() - 1; i >= 0; --i) {
		nowValue = romanValue[FindSymbol(roman[i])];
		arabic += (nowValue < previous ? -nowValue : nowValue);
		previous = nowValue;
	}
	return arabic;
}

string ArabicToRoman(int arabic) {
	string roman = "";
	if (arabic == 0)
		return "ZERO";
	for (int i = 12; i >= 0; --i) {
		while (arabic >= combineValue[i]) {
			arabic -= combineValue[i];
			roman += combination[i];
		}
	}
	return roman;
}

int main() {
	cin.sync_with_stdio(false); cin.tie(nullptr);
	string roman1, roman2;
	while (cin >> roman1 >> roman2, roman1 != "#")
		cout << ArabicToRoman(abs(RomanToArabic(roman1) - RomanToArabic(roman2))) << '\n';
}