import java.util.*;

public class Main {
    static HashMap<Character, Integer> romanToInteger = new HashMap<>();
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		romanToInteger.put('I', 1);
		romanToInteger.put('V', 5);
		romanToInteger.put('X', 10);
		romanToInteger.put('L', 50);
		romanToInteger.put('C', 100);
		romanToInteger.put('D', 500);
		romanToInteger.put('M', 1000);
		int sum = 0;
	    int n = sc.nextInt();
	    for (int i = 0; i < n; i++) {
	        sum += getInteger(sc.next());
	    }
	    if (sum >= 4000) {
	        System.out.println("ERROR");
	        return;
	    }
	    StringBuilder sb = new StringBuilder();
	    int first = sum / 1000;
	    for (int i = 0; i < first; i++) {
	        sb.append("M");
	    }
	    int second = sum % 1000 / 100;
	    if (second == 9) {
	        sb.append("CM");
	    } else if (second == 4) {
	        sb.append("CD");
	    } else {
	        if (second >= 5) {
	            second -= 5;
	            sb.append("D");
	        }
	        for (int i = 0; i < second; i++) {
	            sb.append("C");
	        }
	    }
	    int third = sum % 100 / 10;
	    if (third == 9) {
	        sb.append("XC");
	    } else if (third == 4) {
	        sb.append("XL");
	    } else {
	        if (third >= 5) {
	            third -= 5;
	            sb.append("L");
	        }
	        for (int i = 0; i < third; i++) {
	            sb.append("X");
	        }
	    }
	    int forth = sum % 10;
	    if (forth == 9) {
	        sb.append("IX");
	    } else if (forth == 4) {
	        sb.append("IV");
	    } else {
	        if (forth >= 5) {
	            forth -= 5;
	            sb.append("V");
	        }
	        for (int i = 0; i < forth; i++) {
	            sb.append("I");
	        }
	    }
	    System.out.println(sb);
	}
	
    static int getInteger(String s) {
        ArrayDeque<Integer> stack = new ArrayDeque<>();
        for (char c : s.toCharArray()) {
            int x = romanToInteger.get(c);
            if (stack.size() > 0 && stack.peek() < x) {
                stack.push(x - stack.pop());
            } else {
                stack.push(x);
            }
        }
        int ans = 0;
        while (stack.size() > 0) {
            ans += stack.pop();
        }
        return ans;
    }
}