#include <bits/stdc++.h>
using namespace std;
char s[10000];
char ss[50];
int main() {
  int n;
  scanf("%d", &n);
  int x = 1, y = 1;
  for (int i = 1; i <= n - 1; i++) {
    printf("? %d %d %d %d\n", x, y + 1, n, n);
    fflush(stdout);
    scanf("%s", ss + 1);
    if (ss[1] == 'Y')
      s[i] = 'R', y++;
    else
      s[i] = 'D', x++;
  }
  x = n, y = n;
  for (int i = 2 * n - 2; i >= n; i--) {
    printf("? 1 1 %d %d\n", x - 1, y);
    fflush(stdout);
    scanf("%s", ss + 1);
    if (ss[1] == 'Y')
      s[i] = 'D', x--;
    else
      s[i] = 'R', y--;
  }
  printf("! ");
  for (int i = 1; i <= 2 * n - 2; i++) printf("%c", s[i]);
  return 0;
}
