#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 10;
const int maxint = 0x3f3f3f3f;
const int mod = 1e9 + 7;
int n, a[510][510];
char c[10];
int main() {
  int i, j;
  cin >> n;
  i = j = 1;
  while (i + j <= n) {
    a[i][j] = 1;
    if (j < n) {
      cout << "? " << i << " " << j + 1 << " " << n << " " << n << "\n";
      fflush(stdout);
      cin >> c;
      if (c[0] == 'Y')
        j++;
      else
        i++;
    } else
      i++;
  }
  a[i][j] = 1;
  i = j = n;
  while (i + j > n + 2) {
    a[i][j] = 1;
    if (i > 1) {
      cout << "? 1 1 " << i - 1 << " " << j << "\n";
      fflush(stdout);
      cin >> c;
      if (c[0] == 'Y')
        i--;
      else
        j--;
    } else
      j--;
  }
  a[i][j] = 1;
  cout << "! ";
  i = j = 1;
  while (i + j < n + n) {
    if (j < n && a[i][j + 1]) {
      cout << "R";
      j++;
    } else {
      cout << "D";
      i++;
    }
  }
  cout << "\n";
  return 0;
}
