#include <bits/stdc++.h>
using namespace std;
int n;
char s[10], seq[1010];
bool ask(int x1, int y1, int x2, int y2) {
  if (x1 < 1 || y1 < 1) return false;
  printf("? %d %d %d %d\n", x1, y1, x2, y2);
  fflush(stdout);
  scanf("%s", s);
  return s[0] == 'Y';
}
int main() {
  scanf("%d", &n);
  int cnt = 2 * (n - 1), cx = n, cy = n;
  for (int rep = 1; rep < n; ++rep)
    if (ask(1, 1, cx - 1, cy)) {
      --cx;
      seq[cnt--] = 'D';
    } else {
      --cy;
      seq[cnt--] = 'R';
    }
  cnt = 0;
  cx = 1;
  cy = 1;
  for (int rep = 1; rep < n; ++rep) {
    if (ask(cx, cy + 1, n, n)) {
      ++cy;
      seq[++cnt] = 'R';
    } else {
      ++cx;
      seq[++cnt] = 'D';
    }
  }
  printf("! %s", seq + 1);
  return 0;
}
