import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int n = sc.nextInt();
		int total = 0;
		for (int i=0; i<n; i++) {
			total += RomanToArabic(sc.next());
		}
		System.out.println(total>3999?"ERROR":ArabicToRoman(total));
	}
	
	static int RomanToArabic (String s) {
		String[] a = {"IV","IX","XL","XC","CD","CM"};
		String[] b = {"IIII","VIIII","XXXX","LXXXX","CCCC","DCCCC"};
		for (int j=0; j<6; j++) {
			s = s.replaceAll(a[j],b[j]);
		}
		int n = 0;
		int[] number = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
		String[] roma = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
		for (int i=0; i<s.length(); i++) {
			for (int j=0; j<13; j++) {
				if (s.substring(i,i+1).equals(roma[j])) {n += number[j];}
			}
		}
		if (n > 3999) {return -1;}
		else {return n;}
	}
	
	static String ArabicToRoman (int n) {
		if (n<0 || 3999<n) {return "error";}
		int[] number = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
		String[] roma = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
		StringBuilder ans = new StringBuilder();
		for (int i=0; i<13; i++) {
			int ii = n/number[i];
			for (int j=0; j<ii; j++) {
				ans.append(roma[i]);
			}
			n = n%number[i];
		}
		return ans.toString();
	}
}