#include <bits/stdc++.h>
using namespace std;
int n;
template <typename Drake>
void read(Drake &x) {
  x = 0;
  char ch = getchar();
  bool f = 1;
  while (!isdigit(ch)) {
    if (ch == '-') f ^= 1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + (ch ^ 48);
    ch = getchar();
  }
  x *= (2 * f - 1);
}
template <typename Drake>
void write(Drake x) {
  if (x < 0) {
    x = -x;
    putchar('-');
  }
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
template <typename Drake>
void writeln(Drake x) {
  write(x);
  puts("");
}
bool query(int x, int y, int n, int m) {
  cout << "? " << x << " " << y << " " << n << " " << m << endl;
  fflush(stdout);
  string s;
  cin >> s;
  return (s[0] == 'Y');
}
int main() {
  cin >> n;
  string s1, s2;
  int x, y;
  x = 1;
  y = 1;
  for (int i = 0; i < n - 1; ++i) {
    if (y < n && query(x, y + 1, n, n)) {
      ++y;
      s1 = s1 + 'R';
    } else {
      ++x;
      s1 = s1 + 'D';
    }
  }
  x = n;
  y = n;
  for (int i = 0; i < n - 1; ++i) {
    if (x > 1 && query(1, 1, x - 1, y)) {
      --x;
      s2.push_back('D');
    } else {
      --y;
      s2.push_back('R');
    }
  }
  putchar('!');
  putchar(' ');
  for (int i = 0; i < s1.size(); ++i) putchar(s1[i]);
  for (int i = s2.size() - 1; i >= 0; --i) putchar(s2[i]);
  puts("");
  return 0;
}
