//
// Created by yamunaku on 2021/04/01.
//

#include <bits/stdc++.h>
//#include <atcoder/all>

using namespace std;
//using namespace atcoder;

#define rep(i, n) for(ll i = 0; i < (n); i++)
#define repl(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perl(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD9 998244353
#define MOD1 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)
#define CST(x) cout<<fixed<<setprecision(x)

using ll = long long;
using ld = long double;
using vi = vector<int>;
using mti = vector<vector<int>>;
using vl = vector<ll>;
using mtl = vector<vector<ll>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
template<typename T>
using heap = priority_queue<T, vector<T>, function<bool(const T, const T)>>;

int main() {
    //CFS;
    int n;
    cin >> n;
    string s;
    cin >> s;
    ll c = 0;
    rep(i, n) {
        if (s[i] == 'Q') c++;
        else if (s[i] == 'H') {
            cout << -1 << endl;
            return 0;
        }
    }
    repl(i, 1, c + 1) {
        if (i * i == c) {
            vector<string> v;
            rep(j, c / i) {
                v.push_back(s.substr(i * j, i));
            }
            rep(j, v.size()) {
                rep(k, v.size()) {
                    if (v[j] != v[k]) {
                        cout << -1 << endl;
                        return 0;
                    }
                }
            }
            cout << v[0] << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    return 0;
}