#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<long long> moves;
  int x = 1, y = 1;
  while (x + y < n + 1) {
    cout << "? " << x + 1 << " " << y << " " << n << " " << n << endl;
    string r;
    cin >> r;
    if (r == "BAD") return 0;
    if (r == "YES") {
      ++x;
      moves.push_back(0);
    } else {
      ++y;
      moves.push_back(1);
    }
  }
  vector<long long> moves2;
  x = n, y = n;
  while (x + y > n + 1) {
    cout << "? " << 1 << " " << 1 << " " << x << " " << y - 1 << endl;
    string r;
    cin >> r;
    if (r == "BAD") return 0;
    if (r == "YES") {
      --y;
      moves2.push_back(1);
    } else {
      --x;
      moves2.push_back(0);
    }
  }
  cout << "! ";
  for (int i = 0; i < moves.size(); ++i) {
    if (moves[i] == 0)
      cout << 'D';
    else
      cout << 'R';
  }
  for (int i = moves2.size() - 1; i >= 0; --i) {
    if (moves2[i] == 0)
      cout << 'D';
    else
      cout << 'R';
  }
  cout << endl;
}
