import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.HashMap;
import java.util.NoSuchElementException;

class Main {
	public static void main(String[] args) {
		new Main().run();
	}
	
	void run() {
		FastScanner sc=new FastScanner();
		HashMap<String,Integer> toArabic=new HashMap<String, Integer>();
		HashMap<Integer,String> toRoman=new HashMap<Integer, String>();

		int N=sc.nextInt();
		for(int i=0;i<=3;++i) {
			String a="";
			for(int m=0;m<i;++m) {
				a+="M";
			}
			for(int j=0;j<=9;++j) {
				String b="";
				if(j==4)b="CD";
				else if(j==9)b="CM";
				else {
					for(int m=0;m<j%5;++m) {
						b+="C";
					}
					if(j>=5)b="D"+b;
				}
				for(int k=0;k<=9;++k) {
					String c="";
					if(k==4)c="XL";
					else if(k==9)c="XC";
					else {
						for(int m=0;m<k%5;++m) {
							c+="X";
						}
						if(k>=5)c="L"+c;
					}
					for(int l=0;l<=9;++l) {
						String d="";
						if(l==4)d="IV";
						else if(l==9) d="IX";
						else {
							for(int m=0;m<l%5;++m) {
								d+="I";
							}
							if(l>=5)d="V"+d;
						}
						int v=i*1000+j*100+k*10+l;
						toArabic.put(a+b+c+d, v);
						toRoman.put(v, a+b+c+d);
					}
				}
			}
		}
		int cur=0;
		for(int i=0;i<N;++i) {
			cur+=toArabic.get(sc.next());
		}
		if(cur>3999) {
			System.out.println("ERROR");
		}else {
			System.out.println(toRoman.get(cur));
		}
	}
	
	void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}


class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() { return Double.parseDouble(next());}
}