#include <bits/stdc++.h>
using namespace std;
int n;
string ans, ans1;
set<pair<int, int> > a;
bool res(int a, int b, int c, int d) {
  string s;
  cout << "? " << a << ' ' << b << ' ' << c << ' ' << d << endl;
  cin >> s;
  return (s == "YES");
}
signed main() {
  srand(time(0));
  ios_base::sync_with_stdio(false);
  cin.tie();
  cout.tie();
  cin >> n;
  int first = 1, second = 1;
  a.insert({1, 1});
  for (; n - first + n - second >= n;) {
    if (first < n && res(first + 1, second, n, n))
      first++, ans += 'D';
    else
      second++, ans += 'R';
    a.insert({first, second});
  }
  first = second = n;
  pair<int, int> v;
  for (; first + second - 2 >= n;) {
    if (second > 1 && res(1, 1, first, second - 1))
      second--, ans1 += 'R';
    else
      first--, ans1 += 'D';
    if (a.find({first, second}) != a.end()) {
      v = {first, second};
      break;
    }
  }
  cout << "! ";
  first = second = 1;
  for (int i = 0; i < ans.size(); i++) {
    (ans[i] == 'R' ? second : first)++;
    cout << ans[i];
    if (v == pair<int, int>{first, second}) break;
  }
  reverse(ans1.begin(), ans1.end());
  cout << ans1;
  return 0;
}
