M = [ ('I', 1), ('V', 5), ('X', 10), ('L', 50), ('C', 100), ('D', 500), ('M', 1000), ('IV', 4), ('IX', 9), ('XL', 40), ('XC', 90), ('CD', 400), ('CM', 900), ] M = M[::-1] R = [ ('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), ] def rev(val): ret = [] for s, v in R: while val >= v: val -= v ret.append(s) return ''.join(ret) def parse(r): ret = 0 for s, v in M: while True: idx = r.find(s) if idx == -1: break r = r[:idx] + r[idx + len(s):] ret += v return ret def main(): n = int(input()) R = list(input().split()) ans = 0 for r in R: ans += parse(r) if ans > 3999: print('ERROR') else: print(rev(ans)) main()