#include <bits/stdc++.h>
using namespace std;
char re[20];
char ans[1050];
string up, down;
bool query(int y, int x, int v, int u) {
  printf("? %d %d %d %d\n", y, x, v, u);
  fflush(stdout);
  scanf("%s", re);
  return re[0] == 'Y';
}
int main() {
  int n;
  scanf("%d", &n);
  int y = 1, x = 1;
  for (int i = 1; i < n; i++) {
    if (query(y + 1, x, n, n))
      y++, up += "D";
    else
      x++, up += "R";
  }
  y = n, x = n;
  for (int i = 1; i < n; i++) {
    if (query(1, 1, y, x - 1))
      x--, down = "R" + down;
    else
      y--, down = "D" + down;
  }
  strcpy(ans, up.c_str());
  strcat(ans, down.c_str());
  printf("! %s\n", ans);
  return 0;
}
