#include <bits/stdc++.h>
using namespace std;
int n, tt, nowx, nowy, ans[100005];
int dxf[2] = {1, 0};
int dyf[2] = {0, 1};
int dxb[2] = {0, -1};
int dyb[2] = {-1, 0};
string s;
int main() {
  scanf("%d", &n);
  tt = (n - 1) * 2;
  nowx = n, nowy = n;
  for (int t = 0; t < n - 1; t++) {
    for (int i = 0; i < 2; i++) {
      int nx = nowx + dxb[i], ny = nowy + dyb[i];
      fflush(stdout);
      printf("? 1 1 %d %d\n", nx, ny);
      puts("");
      fflush(stdout);
      cout.flush();
      cin >> s;
      if (s[0] == 'Y') {
        ans[tt] = i ^ 1;
        nowx = nx, nowy = ny;
        break;
      }
    }
    tt--;
  }
  nowx = 1, nowy = 1;
  tt = 1;
  for (int t = 0; t < n - 1; t++) {
    for (int i = 0; i < 2; i++) {
      int nx = nowx + dxf[i], ny = nowy + dyf[i];
      fflush(stdout);
      printf("? %d %d %d %d\n", nx, ny, n, n);
      puts("");
      fflush(stdout);
      cout.flush();
      cin >> s;
      if (s[0] == 'Y') {
        ans[tt] = i;
        nowx = nx, nowy = ny;
        break;
      }
    }
    tt++;
  }
  printf("! ");
  for (int i = 1; i <= n * 2 - 2; i++) {
    if (ans[i] == 0)
      printf("D");
    else
      printf("R");
  }
  puts("");
  return 0;
}
