N = int(input())
lsR = input().split()
d1 = {'I':1,'V':5,'X':10,'L':50,'C':100,'D':500,'M':1000}
d2 = {'IV':4,'IX':9,'XL':40,'XC':90,'CD':400,'CM':900}

ans = 0
for i in range(N):
    r = lsR[i]
    n = len(r)
    now = 0
    v = 0
    while now < n:
        if now == n-1:
            v += d1[r[now]]
            now += 1
            continue
        if r[now]+r[now+1] in d2:
            v += d2[r[now]+r[now+1]]
            now += 2
        else:
            v += d1[r[now]]
            now += 1
    ans += v

if ans >= 4000:
    print('ERROR')
    exit()

dall = []
for key,val in d1.items():
    dall.append((val,key))
for key,val in d2.items():
    dall.append((val,key))
dall.sort()
ans2 = ''
while ans != 0:
    v,k = dall[-1]
    if ans >= v:
        ans2 += k
        ans -= v
    else:
        dall.pop()
print(ans2)