#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    map<char,int> roman={{'I',1},{'V',5},{'X',10},{'L',50},{'C',100},{'D',500},{'M',1000}};
    pair<int,string> toroman[]={{1000,"M"},{500,"D"},{400,"CD"},{100,"C"},{50,"L"},{40,"XL"},{10,"X"},{5,"V"},{4,"IV"},{1,"I"}};
    int n;
    cin>>n;
    int sum=0;
    for (int i=0;i<n;i++) {
        string a;
        cin>>a;
        for (int j=0;j<a.size();j++) {
            if (j+1<a.size()&&roman[a[j]]<roman[a[j+1]])
                sum-=roman[a[j]];
            else
                sum+=roman[a[j]];
        }
    }
    if (sum>3999) {
        puts("ERROR");
        return 0;
    }
    string ans;
    for (auto p:toroman) {
        while (sum>=p.first) {
            sum-=p.first;
            ans+=p.second;
        }
    }
    cout<<ans<<endl;
    return 0;
}