#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

int main() {
	std::vector<int> a(256);
	std::string u = "IVXLCDM";
	int v[] = { 1, 5, 10, 50, 100, 500, 1000 };

	auto f = [&](char c) {
		return v[u.find(c)];
	};

	int n;
	std::cin >> n;

	int sum = 0;
	while (n--) {
		std::string s;
		std::cin >> s;
		int val = 0;
		for (int i = s.size() - 1; i >= 0; i--) {
			if (i + 1 < s.size() && f(s[i]) < f(s[i + 1])) {
				val -= f(s[i]);
			} else {
				val += f(s[i]);
			}
		}
		sum += val;
	}

	if (sum >= 4000) {
		std::cout << "ERROR" << std::endl;
		return 0;
	}

	std::string ans;
	for (int i = 6; i >= 0; i -= 2) {
		int cnt = 0;
		while (sum - v[i] >= 0) {
			sum -= v[i];
			cnt++;
		}
		if (cnt == 4) {
			ans += u[i];
			ans += u[i + 1];
		} else if (cnt == 9) {
			ans += u[i];
			ans += u[i + 2];
		} else if (cnt >= 5) {
			ans += u[i + 1];
			ans += std::string(cnt - 5, u[i]);
		} else {
			ans += std::string(cnt, u[i]);
		}
	}
	std::cout << ans << std::endl;
}