#include <bits/stdc++.h>
using namespace std;
int A[505][505];
int n;
bool query(int a, int b, bool rev) {
  if (!rev) {
    cout << "? " << a << " " << b << " " << n << " " << n << endl;
  } else {
    cout << "? 1 1 " << a << " " << b << endl;
  }
  string ans;
  cin >> ans;
  if (ans == "YES")
    return 1;
  else
    return 0;
}
vector<bool> proc, proc2;
int main() {
  cin >> n;
  int x = 1, y = 1;
  int cnt = 2 * n - 2;
  while (x + y <= n) {
    if (y == n or query(x + 1, y, 0)) {
      proc.push_back(0);
      x++;
    } else {
      proc.push_back(1);
      y++;
    }
  }
  x = n, y = n;
  while (x + y >= n + 2) {
    if (x == 1 or query(x, y - 1, 1)) {
      proc2.push_back(1);
      y--;
    } else {
      proc2.push_back(0);
      x--;
    }
  }
  cout << "! ";
  reverse(proc2.begin(), proc2.end());
  for (auto i : proc) {
    if (i == 0)
      cout << "D";
    else
      cout << "R";
  }
  for (auto i : proc2) {
    if (i == 0)
      cout << "D";
    else
      cout << "R";
  }
  fflush(stdout);
}
