import sys

rom_dic = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}

n = input()
rom_nums = input().split()

def r2n(s):
    rs = [rom_dic[x] for x in s]
    s = rs[-1]
    for a, b in zip(rs[:-1], rs[1:]):
        s += -a if a < b else a
    return s

def n2r(n):
    d2r = {0: "", 1: "I", 2: "II", 3: "III", 4: "IV", 9:"IX"}
    rs = []
    a = ["IVX", "XLC", "CDM", "M  "]
    while n:
        n, d = divmod(n, 10)
        if d < 5:
            r = d2r[d]
        elif 5 <= d < 9:
            r = "V" + d2r[d - 5]
        else:
            r = d2r[9]
        rs.append(r.translate(str.maketrans("IVX", a.pop(0))))
    return "".join(reversed(rs))

def main(argv):
    s = sum([r2n(x) for x in rom_nums])
    if s > 3999:
        print("ERROR")
        sys.exit(0)
    print(n2r(s))


if __name__ == "__main__":
    main(sys.argv)