#include "bits/stdc++.h"

#define ALL(a) (a).begin(),(a).end()
#define SORT(c) sort((c).begin(),(c).end())
#define DESCSORT(c) sort(c.begin(), c.end(), greater<int>())

using namespace std;

using LL = long long int;
using LD = long double;

using pii = pair<int, int>;
using pll = pair<LL, LL>;
using pdd = pair<double, double>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<LL>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;

const int INF = (1 << 30) - 1;
const LL INF64 = ((LL)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

const int dy[] = { 0, 1, 0, -1 };
const int dx[] = { 1, 0, -1, 0 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
LL gcd(LL x, LL y) { return y ? gcd(y, x % y) : x; }

const vs romanNum = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
const vi num = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
map<char, int> mp = { { 'M', 1000 },{ 'D', 500 },{ 'C', 100 },{ 'L', 50 },{ 'X', 10 },{ 'V', 5 },{ 'I', 1 } };

int romanNumToNum(string str) {
	const int n = str.size();
	int res = 0;
	for (int i = 0; i < n; i++) {
		res += (i < n - 1 && mp[str[i]] < mp[str[i + 1]] ? -mp[str[i]] : mp[str[i]]);
	}

	return res;
}

string numToRomanNum(int value) {
	string res = "";
	const int n = num.size();
	for (int i = 0; i < n; i++) {
		if (value == 0) return res;

		while (value >= num[i]) {
			res += romanNum[i];
			value -= num[i];
		}
	}

	return res;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	int n;
	cin >> n;

	int sum = 0;
	for (int i = 0; i < n; i++) {
		string r;
		cin >> r;
		sum += romanNumToNum(r);
	}

	cout << (sum > 3999 ? "ERROR" : numToRomanNum(sum)) << endl;
	return 0;
}