#include <bits/stdc++.h>
using namespace std;
bool ask(int x1, int yy, int x2, int y2) {
  printf("? %d %d %d %d\n", x1, yy, x2, y2);
  fflush(stdout);
  char str[5];
  scanf("%s", str);
  return str[0] == 'Y';
}
vector<char> ans1, ans2;
int main() {
  int n;
  scanf("%d", &n);
  int nx = 1, ny = 1;
  for (int i = 1; i < n; i++)
    if (ask(nx, ny + 1, n, n)) {
      ny++;
      ans1.push_back('R');
    } else {
      nx++;
      ans1.push_back('D');
    }
  nx = n;
  ny = n;
  for (int i = 1; i < n; i++)
    if (ask(1, 1, nx - 1, ny)) {
      nx--;
      ans2.push_back('D');
    } else {
      ny--;
      ans2.push_back('R');
    }
  reverse(ans2.begin(), ans2.end());
  printf("! ");
  for (int i = 0; i < ans1.size(); i++) putchar(ans1[i]);
  for (int i = 0; i < ans2.size(); i++) putchar(ans2[i]);
  printf("\n");
  return 0;
}
