from itertools import *
from bisect import *
# from math import *
from collections import *
from heapq import *
from random import *
from decimal import *
import numpy as np
import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def MF(): return map(float, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LF(): return list(map(float, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]

def main():
    def rtoa(roman):
        res = 0
        for r in roman:
            if r == "I": res += 1
            if r == "V": res += 5
            if r == "X": res += 10
            if r == "L": res += 50
            if r == "C": res += 100
            if r == "D": res += 500
            if r == "M": res += 1000
        res -= 2 * (roman.count("IV") + roman.count("IX"))
        res -= 20 * (roman.count("XL") + roman.count("XC"))
        res -= 200 * (roman.count("CD") + roman.count("CM"))
        return res

    n = II()
    rr = input().split()
    s=0
    for roman in rr:
        s+=rtoa(roman)
    if s>3999:
        print("ERROR")
        exit()
    ans=""
    p,s=divmod(s,1000)
    ans+="M"*p
    p,s=divmod(s,100)
    if p==9:ans+="CM"
    elif p>=5:ans+="D"+"C"*(p-5)
    elif p==4:ans+="CD"
    else:ans+="C"*p
    p,s=divmod(s,10)
    if p==9:ans+="XC"
    elif p>=5:ans+="L"+"X"*(p-5)
    elif p==4:ans+="XL"
    else:ans+="X"*p
    p=s
    if p==9:ans+="IX"
    elif p>=5:ans+="V"+"I"*(p-5)
    elif p==4:ans+="IV"
    else:ans+="I"*p
    print(ans)

main()