/* -*- coding: utf-8 -*-
 *
 * 518.cc: No.518 ローマ数字の和 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_S = 3999;

/* typedef */

/* global variables */

int rcs[256];

/* subroutines */

int rm2i(string &s) {
  int sum = 0, pi = 0;
  for (int i = 0; i < s.size(); i++) {
    int k = rcs[s[i]];
    if (pi < k) sum -= pi * 2;
    sum += k;
    pi = k;
  }
  return sum;
}

string i2rm(int n) {
  string w;
  while (n > 0) {
    if (n >= 1000) w += 'M', n -= 1000;
    else if (n >= 900) w += 'C', w += 'M', n -= 900;
    else if (n >= 500) w += 'D', n -= 500;
    else if (n >= 400) w += 'C', w += 'D', n -= 400;
    else if (n >= 100) w += 'C', n -= 100;
    else if (n >= 90) w += 'X', w += 'C', n -= 90;
    else if (n >= 50) w += 'L', n -= 50;
    else if (n >= 40) w += 'X', w += 'L', n -= 40;
    else if (n >= 10) w += 'X', n -= 10;
    else if (n >= 9) w += 'I', w += 'X', n -= 9;
    else if (n >= 5) w += 'V', n -= 5;
    else if (n >= 4) w += 'I', w += 'V', n -= 4;
    else w += 'I', n--;
  }
  return w;
}

/* main */

int main() {
  rcs['I'] = 1;
  rcs['V'] = 5;
  rcs['X'] = 10;
  rcs['L'] = 50;
  rcs['C'] = 100;
  rcs['D'] = 500;
  rcs['M'] = 1000;

  int n;
  cin >> n;

  int sum = 0;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    int k = rm2i(s);
    sum += k;
    //printf("%s = %d\n", s.c_str(), k);
  }

  if (sum > MAX_S)
    puts("ERROR");
  else
    puts(i2rm(sum).c_str());

  return 0;
}