#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 500;
const int M = 1e6 + 500;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int LOG = 20;
const int OFF = (1 << LOG);
const double EPS = 1e-9;
const double PI = 3.1415926535;
int n, m, x = 1, y = 1, j;
int cnt[N];
string sol, sol2;
bool ask(int x, int y, int z) {
  if (z == 0) {
    cout << "? " << x << " " << y << " " << n << " " << n << " " << endl;
    string res;
    cin >> res;
    if (res[0] == 'Y') return 1;
    return 0;
  }
  if (z == 1) {
    cout << "? " << 1 << " " << 1 << " " << x << " " << y << " " << endl;
    string res;
    cin >> res;
    if (res[0] == 'Y') return 1;
    return 0;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  while (n - x + n - y - 1 >= n - 1) {
    if (x + 1 <= n && ask(x + 1, y, 0)) {
      x++;
      sol.push_back('D');
    } else {
      y++;
      sol.push_back('R');
    }
  }
  x = n, y = n;
  while (x - 1 + y - 1 - 1 >= n - 1) {
    if (y - 1 >= 1 && ask(x, y - 1, 1)) {
      y--;
      sol2.push_back('R');
    } else {
      x--;
      sol2.push_back('D');
    }
  }
  reverse(sol2.begin(), sol2.end());
  sol += sol2;
  cout << "! " << sol << endl;
  return 0;
}
