# coding: utf-8
import array, bisect, collections, copy, heapq, itertools, math, random, re, string, sys, time

sys.setrecursionlimit(10 ** 7)
INF = 10 ** 20
MOD = 10 ** 9 + 7


def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


roman_table = [
    ("M", 1000),
    ("CM", 900),
    ("D", 500),
    ("CD", 400),
    ("C", 100),
    ("XC", 90),
    ("L", 50),
    ("XL", 40),
    ("X", 10),
    ("IX", 9),
    ("IV", 4),
    ("I", 1),
]


def roman_to_int(str):
    ret_num = 0
    for c, n in roman_table:
        while str.startswith(c):
            str = str[len(c):]
            ret_num += n
    return ret_num


def int_to_roman(num):
    res = ""
    for s, v in roman_table:
        d, num = divmod(num, v)
        res += d * s
    return res


def read():
    N = II()
    R = list(map(str, input().split()))
    return (N, R)


def solve(N, R):
    num_sum = sum(map(roman_to_int, R))
    if num_sum >= 4000:
        return "ERROR"
    else:
        return int_to_roman(num_sum)


def main():
    params = read()
    print(solve(*params))


if __name__ == "__main__":
    main()