#include "bits/stdc++.h"

#define REP(i,n) for(ll i=0;i<n;++i)
#define RREP(i,n) for(ll i=n-1;i>=0;--i)
#define FOR(i,m,n) for(ll i=m;i<n;++i)
#define RFOR(i,m,n) for(ll i=n-1;i>=m;--i)
#define ALL(v) (v).begin(),(v).end()
#define PB(a) push_back(a)
#define UNIQUE(v) v.erase(unique(ALL(v)),v.end());
#define DUMP(v) REP(aa, (v).size()) { cout << v[a]; if (a != v.size() - 1)cout << " "; else cout << endl; }
#define INF 1000000001ll
#define MOD 1000000007ll
#define EPS 1e-9

const int dx[8] = { 1,1,0,-1,-1,-1,0,1 };
const int dy[8] = { 0,1,1,1,0,-1,-1,-1 };


using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
ll max(ll a, int b) { return max(a, ll(b)); }
ll max(int a, ll b) { return max(ll(a), b); }
ll min(ll a, int b) { return min(a, ll(b)); }
ll min(int a, ll b) { return min(ll(a), b); }
///(´・ω・`)(´・ω・`)(´・ω・`)(´・ω・`)(´・ω・`)(´・ω・`)///
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	vi v = { 1,5,10,50,100,500,1000 };
	string s = "IVXLCDM";
	vector<string> r(n);
	REP(i, n)cin >> r[i];
	int sum = 0;
	REP(i, n) {
		int tmp = 0;
		if (r[i].size() == 1)tmp += v[s.find(r[i][0])];
		REP(j, r[i].size() - 1) {
			if (s.find(r[i][j]) < s.find(r[i][j + 1])) {
				tmp += v[s.find(r[i][j + 1])] - v[s.find(r[i][j])];
				++j;
			}
			else {
				tmp += v[s.find(r[i][j])];
				if(j==r[i].size()-2)tmp += v[s.find(r[i].back())];
			}
		}
		
		sum += tmp;
	}
	if (sum >= 4000)cout << "ERROR" << endl;
	else {
		string ans;
		REP(i, sum / 1000)ans += 'M';
		sum %= 1000;
		RREP(i, 6) {
			if (i % 2 == 1) {
				if (sum >= v[i]&&v[i+1]-v[i-1]>sum) {
					REP(j, sum / v[i])ans += s[i];
					sum -= v[i];
				}
			}
			else {
				if (sum / (v[i + 2] - v[i]) == 1) {
					ans += s[i];
					ans += s[i + 2];
					sum %= v[i];
				}
				if (sum / (v[i + 1] - v[i]) == 1) {
					ans += s[i];
					ans += s[i + 1];

					sum %= v[i];
				}
				REP(j, sum / v[i])ans += s[i];
				sum %= v[i];
			}
		}
		cout << ans << endl;
	}
	return 0;
}