# -*- coding: utf-8 -*-

def ator(i):
    s = ""
    t4 = i // 1000
    t35 = (i % 1000) // 500
    t3 = (i % 500) // 100
    t25 = (i % 100) // 50
    t2 = (i % 50) // 10
    t15 = i % 10 // 5
    t1 = i % 5

    s += "M" * t4

    if t35 == 1 and t3 == 4:
        s += "CM"
    elif t3 == 4:
        s += "CD"
    else:
        s += "D" * t35 + "C" * t3

    if t25 == 1 and t2 == 4:
        s += "XC"
    elif t2 == 4:
        s += "XL"
    else:
        s += "L" * t25 + "X" * t2

    if t15 == 1 and t1 == 4:
        s += "IX"
    elif t1 == 4:
        s += "IV"
    else:
        s += "V" * t15 + "I" * t1

    return s

def rtoa(s):
    tbx = {'IV' : 4, 'IX' : 9, 'XL' : 40, 'XC' : 90, 'CD' : 400, 'CM' : 900}
    tb = {'I' : 1, 'V' : 5, 'X' : 10, 'L' : 50, 'C' : 100, 'D' : 500, 'M' : 1000}

    sum = 0
    for k in tbx:
        if k in s:
            print s, k, tbx[k]
            sum += tbx[k]
            s = s.replace(k, "")

    for c in s:
        sum += tb[c]
    return sum



def solve(input):
    roma = input[1].split()
    sum = 0
    for r in roma:
        sum += rtoa(r)

    if sum < 4000:
        return ator(sum)
    else:
        return "ERROR"
    pass

if __name__ == "__main__":
    input = []
    input += [raw_input()]
    input += [raw_input()]

    print solve(input)