#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define o(a) cout << a << endl
#define int long long
#define fi first
#define se second
using namespace std;
typedef pair<int, int> P;

const int INF = 1e8;
int d[7] = {1, 5, 10, 50, 100, 500, 1000};
string str = "IVXLCDM";

int change_10(string s){
    int res = 0;
    int now, pre = INF;
    rep(i, 0, s.size()){
        int id = str.find(s[i]);
        now = d[id];
        if(pre < now ){
            res += now - pre;
            pre = INF;
        }else{
            if(pre != INF) res += pre;
            pre = now;
        }
    }
    if(pre != INF) res += pre;
    return res;
}

signed main(){
    int n;
    cin >> n;
    int sum = 0;
    rep(i, 0, n){
        string s;
        cin >> s;
        int tmp = change_10(s);
        sum += tmp;
        // cout << tmp << endl;
    }
    if(sum >= 4000){
        cout << "ERROR" << endl;
        return 0;
    }
    string ans = "";
    if(sum >= 1000){
        rep(i, 0, sum / 1000) ans += str[6];
        sum %= 1000;
    }
    if(sum >= 100){
        int q = sum / 100;
        sum %= 100;
        if(q == 9) ans += "CM";
        else if(q == 4) ans += "CD";
        else{
            if(q >= 5) ans += "D";
            rep(i, 0, q % 5) ans += "C";
        }
    }
    if(sum >= 10){
        int q = sum / 10;
        sum %= 10;
        if(q == 9) ans += "XC";
        else if(q == 4) ans += "XL";
        else{
            if(q >= 5) ans += "L";
            rep(i, 0, q % 5) ans += "X";
        }
    }
    if(sum >= 1){
        int q = sum;
        if(q == 9) ans += "IX";
        else if(q == 4) ans += "IV";
        else{
            if(q >= 5) ans += "V";
            rep(i,0 , q % 5) ans += "I";
        }
    }
    // repb(i, 6, 0){
    //     if(sum < d[i]) continue;
    //     int q = sum / d[i];
    //     sum %= d[i];
    //     // cout <<d[i] << " " << q << " "<< sum << endl;
    //     string tmp = "";
    //     // if(q == 4){
    //     //     tmp += str[i];
    //     //     tmp += str[i + 1];
    //     //     // cout << 1 <<  " " << tmp << endl;
    //     // }else{
    //         rep(j, 0, q){
    //             tmp += str[i];
    //         }
    //     // }
    //     // cout << tmp << endl;
    //     ans += tmp;
    // }
    cout << ans << endl;
}