numeral_map = tuple(zip(
    (1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1),
    ('M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I')
))

def int_to_roman(i):
    result = []
    for integer, numeral in numeral_map:
        count = i // integer
        result.append(numeral * count)
        i -= integer * count
    return ''.join(result)

def roman_to_int(n):
    i = result = 0
    for integer, numeral in numeral_map:
        while n[i:i + len(numeral)] == numeral:
            result += integer
            i += len(numeral)
    return result

def main():
    n = int(input())
    ans = 0
    for r in input().split():
        ans += roman_to_int(r)
    if ans > 3999:
        print('ERROR')
    else:
        print(int_to_roman(ans))
main()