#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 2147483600
#define long long long // for codeforces

//めんどうなので放置

string aa [] = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
int bb [] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
// 13

string encode(int x){
  string res = "";
  rep(i,13){
    while(x >= bb[i]){
      res += aa[i];
      x -= bb[i];
    }
  }
  return res;
}

int decode(string &str){
  int res = 0;
  rep(i,13){
    while(str.find(aa[i]) == 0){
      str = str.substr(aa[i].size());
      res += bb[i];
    }
  }
  return res;
}

int main(){
  int n;
  cin>>n;
  vector<string> vec(n);
  rep(i,n) cin>>vec[i];

  int x=0;
  rep(i,n) x += decode(vec[i]);

  if(x>=4000) cout << "ERROR" << endl;
  else cout << encode(x) << endl;

  return 0;
}