#include <bits/stdc++.h>
using namespace std;
int n;
bool query(int x, int y) {
  if (x < 1 || x > n) return 0;
  if (y < 1 || y > n) return 0;
  if (x + y >= n + 1) {
    printf("? 1 1 %d %d\n", x, y);
    cout.flush();
  } else {
    printf("? %d %d %d %d\n", x, y, n, n);
    cout.flush();
  }
  string s;
  cin >> s;
  return s == string("YES");
}
int main() {
  cin >> n;
  string ansL, ansR;
  int x = 1, y = 1;
  while (x + y < n) {
    if (query(x, y + 1))
      y++, ansL.push_back('R');
    else
      x++, ansL.push_back('D');
  }
  {
    printf("? %d %d %d %d\n", x, y + 1, n, n);
    cout.flush();
    string s;
    cin >> s;
    if (s == string("YES"))
      y++, ansL.push_back('R');
    else
      x++, ansL.push_back('D');
  }
  x = n, y = n;
  while (x + y > n + 2) {
    if (query(x - 1, y))
      x--, ansR.push_back('D');
    else
      y--, ansR.push_back('R');
  }
  {
    printf("? %d %d %d %d\n", 1, 1, x - 1, y);
    cout.flush();
    string s;
    cin >> s;
    if (s == string("YES"))
      x--, ansR.push_back('D');
    else
      y--, ansR.push_back('R');
  }
  reverse(ansR.begin(), ansR.end());
  cout << "! " << ansL << ansR << '\n';
}
