#include <bits/stdc++.h>

using namespace std;

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

string conv(int x, int d) {
  char one[] = {'I', 'X', 'C', 'M'};
  char five[] = {'V', 'L', 'D', '?'};
  if (x == 0) return "";
  else if (x < 4) return string(x, one[d]);
  else if (x == 4) return string(1, one[d]) + string(1, five[d]);
  else if (x == 5) return string(1, five[d]);
  else if (x < 9) return string(1, five[d]) + string(x-5, one[d]);
  else return string(1, one[d]) + string(1, one[d+1]);
}

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

  map<string, int> decoder;
  map<int, string> encoder;

  for (int i = 1; i < 4000; i++) {
    int x = i;
    string y = "";
    for (int d = 0; d < 4; d++) {
      y = conv(x % 10, d) + y;
      x /= 10;
    }
    encoder[i] = y;
    decoder[y] = i;
  }

  int n;
  cin >> n;

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

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