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 e,i in enumerate([1000,100,10,1]):
    x = ans//i
    ans %= i
    index = e*2
    if x==9:
        kaito += lst[index+1] + lst[index-1]
    elif x>=5:
        kaito += lst[index] + lst[index+1]*(x-5)
    elif x==4:
        kaito += lst[index+1] + lst[index]
    else:
        kaito += lst[index+1]*x

print(kaito)