#include <bits/stdc++.h>
using namespace std;
int dist(pair<int, int>& a, pair<int, int>& b) {
  return abs(a.first - b.first) + abs(a.second - b.second);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  ;
  int n;
  cin >> n;
  pair<int, int> curr_up, curr_down;
  curr_up = {1, 1};
  curr_down = {n, n};
  vector<vector<bool>> way(n + 1, vector<bool>(n + 1));
  way[1][1] = 1;
  way[n][n] = 1;
  stack<pair<int, int>> st;
  st.push({1, 1});
  while (dist(curr_up, curr_down) >= n) {
    string ans;
    if (curr_up.first + 1 <= n) {
      cout << "? " << curr_up.first + 1 << " " << curr_up.second << " "
           << curr_down.first << " " << curr_down.second << endl;
      cin >> ans;
      if (ans == "BAD") return 0;
    }
    if (curr_up.first + 1 <= n && ans == "YES") {
      way[curr_up.first + 1][curr_up.second] = 1;
      st.push({curr_up.first + 1, curr_up.second});
      ++curr_up.first;
    } else {
      cout << "? " << curr_up.first << " " << curr_up.second + 1 << " "
           << curr_down.first << " " << curr_down.second << endl;
      cin >> ans;
      if (ans == "BAD") return 0;
      way[curr_up.first][curr_up.second + 1] = 1;
      st.push({curr_up.first, curr_up.second + 1});
      ++curr_up.second;
    }
  }
  pair<int, int> fin = curr_up;
  while (curr_down != fin) {
    string ans;
    st.pop();
    pair<int, int> curr = st.top();
    if (curr_down.second - 1 >= 0) {
      cout << "? " << curr.first << " " << curr.second << " " << curr_down.first
           << " " << curr_down.second - 1 << endl;
      cin >> ans;
      if (ans == "BAD") return 0;
    }
    if (curr_down.second - 1 >= 0 && ans == "YES") {
      way[curr_down.first][curr_down.second - 1] = 1;
      --curr_down.second;
    } else {
      cout << "? " << curr.first << " " << curr.second << " "
           << curr_down.first - 1 << " " << curr_down.second << endl;
      cin >> ans;
      if (ans == "BAD") return 0;
      way[curr_down.first - 1][curr_down.second] = 1;
      --curr_down.first;
    }
  }
  curr_up = {1, 1};
  curr_down = {n, n};
  cout << "! ";
  while (curr_up != curr_down) {
    if (curr_up.first + 1 <= n && way[curr_up.first + 1][curr_up.second]) {
      cout << 'D';
      ++curr_up.first;
    } else {
      cout << 'R';
      ++curr_up.second;
    }
  }
  cout << endl;
  return 0;
}
