#yuki_518

l=[(1000, 'M'), (900, 'CM'), (500, 'D'), (400, 'CD'), (100, 'C'), (90, 'XC'),(50, 'L'), (40, 'XL'), (10, 'X'), (9, 'IX'), (5, 'V'), (4, 'IV'), (1, 'I')]

def roman2int(s):
 res=0
 a=[]
 for i in range(len(s)):
  for j in xrange(len(l)):
   if s[i]==l[j][1]:
    a.append(l[j][0])
 a.append(0)
 for i in range(len(s)):
  if a[i]>=a[i+1]:
   res+=a[i]
  else:
   res-=a[i]
 return res

def int2roman(n):
 res = ''
 for num, roman in l:
  res+=roman*(n/num)
  n%=num
 return res

n=int(raw_input())
lr=raw_input().split()
li=[]
for i in xrange(n):
 li.append(roman2int(lr[i]))
sm=sum(li)
if sm>3999:
 print 'ERROR'
else:
 print int2roman(sm)