d = {"IV":4,"IX":9,"XL":40,"XC":90,"CD":400,"CM":900}
dd = dict(zip("IVXLCDM",[1,5,10,50,100,500,1000]))

def r2i(s):
    x = 0
    for k in d:
        if k in s:
            x += d[k]
            s = s.replace(k,"")
    for k in dd:
        x += dd[k]*s.count(k)
    return x

def i2r(x):
    if x >= 4000: return "ERROR"
    s = []
    for k,v in zip([1000,900,500,400,100,90,50,40,10,9,5,4,1],["M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"]):
        if x >= k:
            s.append(v*(x//k))
            x %= k
    return "".join(s)

n = int(input())
r = input().split()
x = sum(r2i(ri) for ri in r)
print(i2r(x))