#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma warning(disable : 4996)
#pragma comment(linker, "/STACK:336777216")
using namespace std;
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, 1, -1};
const int ddx[8] = {0, 0, 1, 1, 1, -1, -1, -1},
          ddy[8] = {1, -1, 1, 0, -1, 1, 0, -1};
const int INF = 0x3f7f7f7f;
const long long INF_LL = 0x3f7f7f7f7f7f7f7f;
long long POW(long long a, long long b, long long MMM) {
  long long ret = 1;
  for (; b; b >>= 1, a = (a * a) % MMM)
    if (b & 1) ret = (ret * a) % MMM;
  return ret;
}
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
long long LCM(long long a, long long b) {
  if (a == 0 || b == 0) return a + b;
  return a / GCD(a, b) * b;
}
long long INV(long long a, long long m) {
  long long m0 = m, y = 0, x = 1;
  if (m == 1) return 0;
  while (a > 1) {
    long long q = a / m;
    long long t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0) x += m0;
  return x;
}
pair<long long, long long> EXGCD(long long a, long long b) {
  if (b == 0) return {1, 0};
  auto t = EXGCD(b, a % b);
  return {t.second, t.first - t.second * (a / b)};
}
bool OOB(long long x, long long y, long long N, long long M) {
  return 0 > x || x >= N || 0 > y || y >= M;
}
int N;
void ask1(int x1, int y1) {
  cout << "? " << x1 << ' ' << y1 << ' ' << N << ' ' << N << endl;
}
void ask2(int x1, int y1) {
  cout << "? " << 1 << ' ' << 1 << ' ' << x1 << ' ' << y1 << endl;
}
string ans;
string ans2;
int curX = 1;
int curY = 1;
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N;
  while (curX + curY < N + 1) {
    ask1(curX, curY + 1);
    string recv;
    cin >> recv;
    if (recv == "YES") {
      curY++;
      ans += 'R';
    } else {
      curX++;
      ans += 'D';
    }
  }
  int xx = N;
  int yy = N;
  while (xx + yy > N + 1) {
    ask2(xx - 1, yy);
    string recv;
    cin >> recv;
    if (recv == "YES") {
      xx--;
      ans2 += 'D';
    } else {
      yy--;
      ans2 += 'R';
    }
  }
  reverse((ans2).begin(), (ans2).end());
  cout << "! " << ans + ans2 << endl;
}
