#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	
	int num[] = {1, 5, 10, 50, 100, 500, 1000};
	string roma = "IVXLCDM";
	map<char, int> conv;
	REP(i, roma.size()) conv[roma[i]] = i;
	
	auto decode = [&](const string & R) -> int {
		int res = 0, prv = INF;
		REP(i, R.size()) {
			int cur = num[conv[R[i]]];
			if (prv < cur) { res += cur - prv; prv = INF; }
			else if (prv == cur) prv += cur;
			else {
				if (prv != INF) res += prv;
				prv = cur;
			}
		}
		if (prv != INF) res += prv;
		return res;
	};
	
	auto encode = [&](int n) -> string {
		string res;
		for (int i = 6; i >= 0; --i) {
			int cur = n / num[i];
			n -= cur * num[i];
			
			if (cur == 4) {
				res += "I";
				res += roma[i];
			}
			else res += string(cur, roma[i]);
		}
		return res;
	};
	
	int ans = 0;
	REP(i, N) {
		string s;
		cin >> s;
		ans += decode(s);
	}
	if (ans > 3999) puts("ERROR");
	else cout << encode(ans) << endl;
}