#include <bits/stdc++.h>
using namespace std;
char s[1000];
int ask(int r1, int c1, int r2, int c2) {
  printf("? %d %d %d %d\n", r1, c1, r2, c2);
  fflush(stdout);
  scanf("%s", s);
  if (s[0] == 'Y') return 1;
  return 0;
}
int a[1000][1000];
int main() {
  int n;
  scanf("%d", &n);
  int x = 1, y = 1;
  for (int i = 1; i < n; i += 1) {
    a[x][y] = 1;
    if (ask(x + 1, y, n, n))
      x += 1;
    else
      y += 1;
  }
  a[x][y] = 1;
  x = n, y = n;
  for (int i = 1; i < n; i += 1) {
    a[x][y] = 1;
    if (ask(1, 1, x, y - 1))
      y -= 1;
    else
      x -= 1;
  }
  a[x][y] = 1;
  printf("! ");
  x = 1, y = 1;
  for (int i = 0; i < 2 * n - 2; i += 1) {
    if (x == n && y == n) break;
    if (a[x + 1][y] == 1) {
      printf("D");
      x += 1;
    } else {
      printf("R");
      y += 1;
    }
  }
  printf("\n");
  fflush(stdout);
}
