import sys

rom_dic = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
n = input()
rom_nums = input().split()
s = 0

for rom_num in rom_nums:
    ara_num = [rom_dic[x] for x in rom_num]
    s += ara_num[-1]
    for a, b in zip(ara_num[:-1], ara_num[1:]):
        s += -a if a < b else a

if s > 3999:
    print("ERROR")
    sys.exit(0)

d2r = {5:"V", 10:"X"}
rom_sum = []
trans = ["IVX", "XLC", "CDM", "M  "]
while s:
    s, d = divmod(s, 10)
    r = "I" * d if d < 4 else "V" + "I" * (d - 5) if 4 < d < 9 else "I" + d2r[d + 1]
    rom_sum.append(r.translate(str.maketrans("IVX", trans.pop(0))))
print("".join(reversed(rom_sum)))