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

map<char,int> mp;

int to_int(string s){
	int prev = 0,sum = 0;
	for(int i = s.length() - 1;i >= 0;i--){
		int add = mp[s[i]];
		if(add < prev) sum -= add;
		else sum += add;
		prev = add;
	}
	return sum;
}

string to_rome(int n){
	string s;
	char c[] = {'C','X','I'},cc[] = {'M','D','C','L','X','V'};
	int num = 1000;
	for(int i = 0;i < 3;i++){
		if(n % num == num - num / 10){
			s += c[i];
			n += num / 10;
		}
		for(int j = 0;j < n / num;j++) s += cc[i * 2];
		n %= num;
		if(n % (num / 2) == num / 2 - num / 10){
			s += c[i];
			n += num / 10;
		}
		if(n >= num / 2) s += cc[i * 2 + 1];
		n %= num / 2;
		num /= 10;
	}
	for(int i = 0;i < n;i++) s += 'I';
	return s;
}

int main(){
	int n;
	cin >> n;
	mp['I'] = 1;
	mp['V'] = 5;
	mp['X'] = 10;
	mp['L'] = 50;
	mp['C'] = 100;
	mp['D'] = 500;
	mp['M'] = 1000;
	int ans = 0;
	for(int i = 0;i < n;i++){
		string s;
		cin >> s;
		ans += to_int(s);
	}
	if(ans >= 4000) cout << "ERROR" << endl;
	else cout << to_rome(ans) << endl;
	return 0;
}