#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
using namespace std;

int main()
{
	map<char, int>roma;
	roma['I'] = 1;
	roma['V'] = 5;
	roma['X'] = 10;
	roma['L'] = 50;
	roma['C'] = 100;
	roma['D'] = 500;
	roma['M'] = 1000;


	int N; cin >> N;
	vector<string>S(N);
	for (int i = 0; i < N; i++) {
		cin >> S[i];
	}


	int sum = 0;
	for (int i = 0; i < N; i++) {
		int num = 0;
		int maxRoma = 0;
		for (int j = S[i].size()-1; j >= 0; j--) {
			if (maxRoma > roma[S[i][j]]) {
				num -= roma[S[i][j]];
			}
			else {
				num += roma[S[i][j]];
				maxRoma = max(maxRoma, roma[S[i][j]]);
			}
		}
		sum += num;
	}

	if (sum > 3999)cout << "ERROR" << endl;
	else {
		string s = "";
		if (sum >= 1000) {
			int M = sum / 1000;
			sum %= 1000;
			for (int i = 0; i < M; i++)s += "M";
		}
		if (sum >= 900) {
			s += "CM";
			sum -= 900;
		}
		if (sum >= 500) {
			s += "D";
			sum -= 500;
		}
		if (sum >= 400) {
			s += "CD";
			sum -= 400;
		}
		if (sum >= 100) {
			int C = sum / 100;
			sum %= 100;
			for (int i = 0; i < C; i++)s += "C";
		}
		if (sum >= 90) {
			s += "XC";
			sum -= 90;
		}
		if (sum >= 50) {
			s += "L";
			sum -= 50;
		}
		if (sum >= 40) {
			s += "XL";
			sum -= 40;
		}
		if (sum >= 10) {
			int X = sum / 10;
			sum %= 10;
			for (int i = 0; i < X; i++)s += "X";
		}
		if (sum >= 9) {
			s += "IX";
			sum -= 9;
		}
		if (sum >= 5) {
			s += "V";
			sum -= 5;
		}
		if (sum >= 4) {
			s += "IV";
			sum -= 4;
		}
		if (sum >= 1) {
			int I = sum / 1;
			sum %= 1;
			for (int i = 0; i < I; i++)s += "I";
		}

		cout << s << endl;
	}

    return 0;
}