#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int> > b, e;
int main() {
  int n;
  cin >> n;
  int ex = n, ey = n;
  e.push_back({ex, ey});
  while (ex - 1 + ey - 1 >= n) {
    cout << "? 1 1 " << ex - 1 << " " << ey << "\n";
    cout.flush();
    string re;
    cin >> re;
    if (re == "YES")
      ex--;
    else
      ey--;
    e.push_back({ex, ey});
  }
  int bx = 1, by = 1;
  b.push_back({bx, by});
  while (n - bx + n - by >= n) {
    cout << "? " << bx << " " << by + 1 << " " << n << " " << n << "\n";
    cout.flush();
    string re;
    cin >> re;
    if (re == "YES")
      by++;
    else
      bx++;
    b.push_back({bx, by});
  }
  cout << "! ";
  for (int i = 1; i < b.size(); i++)
    if (b[i].first > b[i - 1].first)
      cout << "D";
    else
      cout << "R";
  for (int i = e.size() - 1; i > 0; i--)
    if (e[i - 1].first > e[i].first)
      cout << "D";
    else
      cout << "R";
  cout.flush();
}
