import strutils,sequtils,tables
var
    N : int
    R : seq[string]
    cnt : int
    Roman = {'I': 1, 'V': 5, 'X': 10, 'L':50, 'C':100,'D' :500 ,'M':1000}.toTable
cnt = 0
N = stdin.readline.parseInt
R = stdin.readline.strip.split
for r in R:
    for i in 0..r.len-2:
        if Roman[r[i]] < Roman[r[i + 1]]:
            cnt -= Roman[r[i]]
        else:
            cnt += Roman[r[i]]
    cnt += Roman[r[^1]]
if cnt > 3999:
    echo "ERROR"
else:
    type rom = tuple[R : string, num :int]
    var
        ans = ""
        rom_num : array[13,rom]
    rom_num = [("M",1000),("CM",900),("D",500),("CD",400),("C",100),("XC",90),("L",50),("XL",40),("X",10),("IX",9),("V",5),("IV",4),("I",1)]
    for r in rom_num:
        while cnt >= r[1]:
            ans &= r[0]
            cnt -= r[1]
    echo ans