D = {"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000}
N = int(input())
A = list(input().split())
cnt = 0
for j in range(N):
    r = A[j]
    for i in range(len(r)-1):
        if D[r[i]]>=D[r[i+1]]:
            cnt += D[r[i]]
        else:
            cnt -= D[r[i]]
    cnt += D[r[-1]]
if cnt>=4000:
    print("ERROR")
else:
    ans = ""
    r = cnt
    q = r//1000
    r = r%1000
    ans += "M"*q
    q = r//100
    r = r%100
    if q==9:
        ans += "CM"
    elif q>=5:
        ans += "D"+"C"*(q-5)
    elif q==4:
        ans += "CD"
    else:
        ans += "C"*q
    q = r//10
    r = r%10
    if q==9:
        ans += "XC"
    elif q>=5:
        ans += "L"+"X"*(q-5)
    elif q==4:
        ans += "XL"
    else:
        ans += "X"*q
    if r==9:
        ans += "IX"
    elif r>=5:
        ans += "V"+"I"*(r-5)
    elif r==4:
        ans += "IV"
    else:
        ans += "I"*r
    print(ans)