def roman(n,s):
    roman=["M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"]
    arabic=[1000,900,500,400,100,90,50,40,10,9,5,4,1]
    number=[0 for i in range(n)]

    for i in range(n):
      j=0
      while j<len(s[i]):
        for k in range(len(roman)):
            if  len(roman[k])==1 and str((s[i]))[j]==roman[k]:
                number[i]+=arabic[k]
                j+=1
                break
            elif j<len(s[i])-1:
              if  len(roman[k])==2 and str((s[i]))[j]+str((s[i]))[j+1]==roman[k]:
                number[i]+=arabic[k]
                j+=2
                break
    
    ans_arabic=sum(number)
    ans_roman=""
    m=0
    if ans_arabic>=4000:
        print("ERROR")
    else:
      while ans_arabic>0:
        if ans_arabic>=arabic[m]:
            ans_roman+=roman[m]
            ans_arabic-=arabic[m]
        else:
            m+=1
    print(ans_roman)

n=int(input())
s=input().split()
roman(n,s)