#include <bits/stdc++.h>
using namespace std;
int cnt[10004];
int n;
bool query(int x1, int x2, int t) {
  if (t) {
    printf("? %d %d %d %d\n", 1, 1, x1, x2);
  } else {
    printf("? %d %d %d %d\n", x1, x2, n, n);
  }
  fflush(stdout);
  char st[10];
  scanf("%s", st);
  return st[0] == 'Y';
}
int main() {
  scanf("%d", &n);
  int x = 1, y = 1;
  int cnt = n - 1;
  string a, b;
  while (cnt--) {
    if (query(x + 1, y, 0)) {
      a += "D";
      x++;
    } else
      y++, a += "R";
  }
  int keepx = x, keepy = y;
  cnt = n - 1;
  x = n, y = n;
  while (cnt--) {
    if (query(x, y - 1, 1)) {
      y--, b += "R";
    } else
      x--, b += "D";
  }
  assert(x == keepx && y == keepy);
  printf("! ");
  reverse(b.begin(), b.end());
  a += b;
  printf("%s\n", a.c_str());
  fflush(stdout);
  return 0;
}
