#include <bits/stdc++.h>
using namespace std;
const int N = 550;
int n, midx, midy;
char s[10];
string S = "", B = "";
int query(int x, int y, int X, int Y) {
  printf("? %d %d %d %d\n", x, y, X, Y);
  fflush(stdout);
  scanf("%s", s);
  return (s[0] == 'Y');
}
int main() {
  scanf("%d", &n);
  int x = 1, y = 1;
  while (x + y < n + 1) {
    if (query(x + 1, y, n, n))
      x++, S = S + 'D';
    else
      y++, S = S + 'R';
  }
  int xx = n, yy = n;
  while (xx + yy > n + 1) {
    if (query(1, 1, xx, yy - 1))
      yy--, B = 'R' + B;
    else
      xx--, B = 'D' + B;
  }
  printf("! ");
  cout << S << B << endl;
  return 0;
}
