#include <bits/stdc++.h>
using namespace std;
map<string, int> decm;
int NUM[13] = {
    1, 4, 5, 9,
    10, 40, 50, 90,
    100, 400, 500, 900,
    1000
};
string SYM[13] = {
    "I", "IV", "V", "IX",
    "X", "XL", "L", "XC",
    "C", "CD", "D", "CM",
    "M"
};

void init() {
    for (int i = 0; i < 13; i++) {
        int num = NUM[i];
        string sym = SYM[i];
        decm[sym] = num;
    }
}

// decode
int dec(string s) {
    int ret = 0;
    for (size_t i = 0; i < s.size(); i++) {
        string f2 = s.substr(i, 2); // first 2 chars
        string f1 = s.substr(i, 1); // first 1 char
        if (i + 1 < s.size() && decm.find(f2) != decm.end()) {
            ret += decm[f2];
            i++; // skip 2 chars
        } else {
            ret += decm[f1];
        }
    }
    return ret;
}

// encode
string enc(int x) {
    if (x == 0) {
        return "ZERO";
    }
    string ret = "";
    for (int i = 12; i >= 0; i--) {
        int num = NUM[i];
        string sym = SYM[i];
        while (x >= num) {
            ret += sym;
            x -= num;
        }
    }
    return ret;
}

int main() {
    init();
    string a, b;
    while (cin >> a && a != "#") {
        cin >> b;
        int ans = abs(dec(a) - dec(b));
        cout << enc(ans) << endl;
    }
}