#include <bits/stdc++.h>
using namespace std;
const long long maxn = 550;
bool khali[maxn][maxn];
long long kj;
long long n;
void dfs(long long x, long long y) {
  if (y == n && x == n) {
    kj++;
    return;
  }
  if (khali[x + 1][y]) {
    cout << 'D';
    kj++;
    dfs(x + 1, y);
  } else {
    cout << 'R';
    dfs(x, y + 1);
  }
  kj++;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  long long x = 1;
  kj++;
  long long y = 1;
  for (long long i = 1; i < n; i++) {
    khali[x][y] = 1;
    if (x != n) {
      cout << '?' << ' ' << x + 1 << ' ' << y << ' ' << n << ' ' << n << endl;
      string r;
      cin >> r;
      kj++;
      if (r == "YES") {
        x++;
      } else {
        y++;
      }
    } else {
      y++;
    }
    khali[x][y] = 1;
  }
  x = n;
  y = n;
  kj++;
  for (long long i = 1; i < n; i++) {
    khali[x][y] = 1;
    if (y != 1) {
      cout << '?' << ' ' << 1 << ' ' << 1 << ' ' << x << ' ' << y - 1 << endl;
      kj++;
      string r;
      cin >> r;
      if (r == "YES") {
        y--;
      } else {
        x--;
      }
      kj++;
    } else {
      x--;
    }
    khali[x][y] = 1;
  }
  kj++;
  cout << "! ";
  dfs(1, 1);
  kj++;
  cout << endl;
  return 0;
}
