#include <iostream.h>
#include <fstream.h>

const char* InputFile = "roman.in";
const char* OutputFile = "roman.out";
const int MaxRoman = 1024;

int value(char symbol)
{
	switch(symbol) {
	case 'I': return 1;
	case 'V': return 5;
	case 'X': return 10;
	case 'L': return 50;
	case 'C': return 100;
	case 'D': return 500;
	case 'M': return 1000;
	}
	return 0;
}

void RomanToInt(char* roman, int& num)
{
	num = 0;
	while(*roman) {
		if(value(roman[0]) >= value(roman[1])) {
			num += value(roman[0]);
		}
		else {
			num -= value(roman[0]);
		}
		roman++;
	}
}

void IntToRoman(char* roman, int num)
{
	struct {
		int s1, s2;
		int div;
	} Table[4] = {
		{ 'M', 0 , 1000 },
		{ 'C', 'D', 100 },
		{ 'X', 'L', 10},
		{ 'I', 'V', 1 },
	};
	int i, j;

	for(i=0; i<4; i++) {
		j = num / Table[i].div;
		num %= Table[i].div;
		switch(j) {
		case 0:
			break;
		case 4:
			*roman++ = Table[i].s1;
			*roman++ = Table[i].s2;
			break;
		case 9:
			*roman++ = Table[i].s1;
			*roman++ = Table[i-1].s1;
			break;
		case 3:
			*roman++ = Table[i].s1;
		case 2:
			*roman++ = Table[i].s1;
		case 1:
			*roman++ = Table[i].s1;
			break;
		default:
			*roman++ = Table[i].s2;
			for(j-=5; j>0; j--) {
				*roman++ = Table[i].s1;
			}
		}
	}
	*roman = 0;
}

void main()
{
	fstream fin, fout;
	char r1[MaxRoman], r2[MaxRoman];
	int n1, n2;

	fin.open(InputFile, ios::in);
	fout.open(OutputFile, ios::out);

	while(fin.good() && fout.good()) {
		fin >> r1;
		if(r1[0] == '#' || !fin.good()) {
			break;
		}
		fin >> r2;
		RomanToInt(r1, n1);
		RomanToInt(r2, n2);
		n1 -= n2;
		if(n1 == 0) {
			fout << "ZERO" << endl;
		}
		else {
			if(n1 < 0) {
				n1 = -n1;
			}
			IntToRoman(r1, n1);
			fout << r1 << endl;
		}
	}
}