#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

vector<int> x = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
vector<string> y = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

string encode(int n) {
  string s;
  for (int i = 0; i < x.size(); i++) {
    while (n >= x[i]) {
      n -= x[i];
      s += y[i];
    }
  }
  return s;
}

int decode(string s) {
  int ret = 0;
  int p = 0;
  for (int i = 0; i < x.size(); i++) {
    while (s.substr(p, y[i].size()) == y[i]) {
      ret += x[i];
      p += y[i].size();
      if (p == s.length())
        break;
    }
  }
  return ret;
}

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

  int n;
  cin >> n;

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

  if (ret >= 4000)
    cout << "ERROR" << endl;
  else
    cout << encode(ret) << endl;
  
  return 0;
}