#include <bits/stdc++.h>
using namespace std;
int n;
char s[9];
const int dx[] = {0, 1, -1, 0};
const int dy[] = {1, 0, 0, -1};
int a[1010], b[1010];
int main() {
  cin >> n;
  int x = 1, y = 1;
  while (x + y - 1 != n) {
    cout << "? " << x + dx[0] << ' ' << y + dy[0] << ' ' << n << ' ' << n
         << endl;
    cin >> s;
    if (s[0] == 'Y')
      x = x + dx[0], y = y + dy[0], a[++a[0]] = 0;
    else
      x = x + dx[1], y = y + dy[1], a[++a[0]] = 1;
  }
  x = n, y = n;
  while (x + y - 1 != n) {
    cout << "? " << 1 << ' ' << 1 << ' ' << x + dx[2] << ' ' << y + dy[2]
         << endl;
    cin >> s;
    if (s[0] == 'Y')
      x = x + dx[2], y = y + dy[2], b[++b[0]] = 2;
    else
      x = x + dx[3], y = y + dy[3], b[++b[0]] = 3;
  }
  cout << "! ";
  for (int i = 1; i <= a[0]; i++)
    if (a[i] == 0)
      cout << "R";
    else
      cout << "D";
  for (int i = b[0]; i >= 1; i--)
    if (b[i] == 2)
      cout << "D";
    else
      cout << "R";
  cout << endl;
  return 0;
}
