# -*- 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):
    sum = 0

    if "IV" in s:
        sum += 4
        s = s.replace("IV", "")

    if "IX" in s:
        sum += 9
        s = s.replace("IX", "")

    if "XL" in s:
        sum += 40
        s = s.replace("XL", "")

    if "XC" in s:
        sum += 90
        s = s.replace("XC", "")

    if "CD" in s:
        sum += 400
        s = s.replace("CD", "")

    if "CM" in s:
        sum += 900
        s = s.replace("CM", "")

    for c in s:
        if c == 'I' :
            sum += 1
        elif c == 'V':
            sum += 5
        elif c == 'X':
            sum += 10
        elif c == 'L':
            sum += 50
        elif c == 'C':
            sum += 100
        elif c == 'D':
            sum += 500
        elif c == 'M':
            sum += 1000
    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)