#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define pi M_PI
#define R cin>>
#define Z class
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
template<Z A>void pr(A a){cout<<a;ln;}
template<Z A,Z B>void pr(A a,B b){cout<<a<<' ';pr(b);}
template<Z A,Z B,Z C>void pr(A a,B b,C c){cout<<a<<' ';pr(b,c);}
template<Z A,Z B,Z C,Z D>void pr(A a,B b,C c,D d){cout<<a<<' ';pr(b,c,d);}
template<Z A>void PR(A a,ll n){rep(i,n){if(i)cout<<' ';cout<<a[i];}ln;}
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1000000007,MAXL=1LL<<61,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<int,int> P;

map<char,int> m;
int N(string s) {
  int ans=0;
  rep(i,s.size()) {
    if(i<s.size()&&m[s[i]]<m[s[i+1]]) ans-=m[s[i]];
    else ans+=m[s[i]];
  }
  return ans;
}

string S(int n) {
  string s="";
  int k=0;
  while(n) {
    int x=n%10;
    if(x==9) {
      if(k==0) s="IX"+s;
      if(k==1) s="XC"+s;
      if(k==2) s="CM"+s;
    } else if(x==4) {
      if(k==0) s="IV"+s;
      if(k==1) s="XL"+s;
      if(k==2) s="CD"+s;
    } else {
      rep(i,x%5) {
        if(k==0) s="I"+s;
        if(k==1) s="X"+s;
        if(k==2) s="C"+s;
        if(k==3) s="M"+s;
      }
      if(x>=5) {
        if(k==0) s="V"+s;
        if(k==1) s="L"+s;
        if(k==2) s="D"+s;
      }
    }
    k++;
    n/=10;
  }
  return s;
}

void Main() {
  m['I']=1,m['V']=5,m['X']=10,m['L']=50,m['C']=100,m['D']=500,m['M']=1000;
  int n;
  cin >> n;
  ll ans=0;
  string s[n];
  rep(i,n) {
    cin >> s[i];
    ans+=N(s[i]);
    if(ans>3999) {
      pr("ERROR");
      return;
    }
  }
  pr(S(ans));
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}