#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 100;
void ask(int r1, int c1, int r2, int c2) {
  cout << "? " << r1 << " " << c1 << " " << r2 << " " << c2 << '\n';
  cout.flush();
}
bool ans() {
  string ans;
  cin >> ans;
  return ans == "YES";
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  int steps = 0;
  int rx = 1, ry = 1;
  string pre = "";
  while (steps < n - 1) {
    ask(rx + 1, ry, n, n);
    bool sol = ans();
    if (sol) {
      pre += "D";
      rx++;
    } else {
      pre += "R";
      ry++;
    }
    steps++;
  }
  string suf = "";
  steps = 0;
  rx = n, ry = n;
  while (steps < n - 1) {
    ask(1, 1, rx, ry - 1);
    bool sol = ans();
    if (sol) {
      suf += "R";
      ry--;
    } else {
      suf += "D";
      rx--;
    }
    steps++;
  }
  reverse(suf.begin(), suf.end());
  cout << "! " << (pre + suf) << '\n';
  cout.flush();
}
