Rs = {"I": 1, "V": 5, "X":10, "L": 50, "C": 100, "D": 500, "M": 1000}

def RtoInt(Ri): #Ri: str
    key = list(Ri)
    value = [Rs[i] for i in key]
    for k in range(len(value) - 1):
        if value[k] < value[k + 1]:
            value[k] = -1 * value[k]
    return sum(value)

def InttoR(n):
    strn = str(n)
    res = ""
    for i in range(len(strn)):
        numi = int(strn[- i - 1])
        if numi == 4:
            if i == 0:
                res = "IV" + res
            elif i == 1:
                res = "XL" + res
            elif i == 2:
                res = "CD" + res
        elif numi == 9:
            if i == 0:
                res = "IX" + res
            elif i == 1:
                res = "XC" + res
            elif i == 2:
                res = "CM" + res
        elif numi > 4:
            if i == 0:
                res = "V" + "I" * (numi-5)  + res
            elif i == 1:
                res = "L" + "X" * (numi-5)  + res
            elif i == 2:
                res = "D" + "C" * (numi-5)  + res
        elif numi < 4:
            if i == 0:
                res = "I" * numi + res
            elif i == 1:
                res = "X" * numi + res
            elif i == 2:
                res = "C" * numi + res
            elif i == 3:
                res = "M" * numi + res
    return res

N = int(input())
R = list(input().split(" "))
#N = 5
#R = list("IV XXI CCCXL III MMCMVI".split())

Rint = list(map(RtoInt, R))
sumR = sum(Rint)
if sumR > 3999:
    print("ERROR")
else:
    print(InttoR(sumR))