import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
A=list(input().split())
D={"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000}
Dec={"IV","IX","XL","XC","CD","CM"}
ans=0
def f(S):
	lgt=len(S)
	ret=0
	for i in range(lgt):
		s=S[i]
		if i<lgt-1 and S[i]+S[i+1] in Dec:
			ret-=D[s]
		else:
			ret+=D[s]
	return ret
for a in A:
	ans+=f(a)

if ans>=4000:
	print("ERROR")
else:
	ans2="M"*(ans//1000)
	XYZ=[("M","D","C"),("C","L","X"),("X","V","I")]
	for i in range(3):
		a=(ans%(10**(3-i)))//(10**(2-i))
		X,Y,Z=XYZ[i]
		if a<=3:
			ans2+=Z*a
		elif a==4:
			ans2+=Z+Y
		elif a<=8:
			ans2+=Y+Z*(a-5)
		else:
			ans2+=Z+X
	print(ans2)