n = int(input())
dic = {"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000}
lst = ["M","D","C","L","X","V","I"]
num = list(input().split())
ans = 0
kaito = ""

for i in num:
    tmp = [dic[i[0]]]
    for index in range(1,len(i)):
        x = dic[i[index]]
        if tmp[-1]<x:
            tmp[-1] = -tmp[-1]
        tmp.append(x)
    ans += sum(tmp)

if ans>3999:
    print("ERROR")
    exit(0)

for i,s in enumerate(lst):
    x = dic[s]
    y = ans//x
    if y==4:
        kaito += lst[i] + lst[i-1]
    elif y>0:
        kaito += lst[i]*y
    ans -= x*y

print(kaito)