#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
char t[20];
char ans[1050];
int main() {
  int n;
  scanf("%d", &n);
  int curx = n, cury = n;
  for (int i = n * 2 - 1; i >= n + 1; --i) {
    printf("? %d %d %d %d\n", 1, 1, curx - 1, cury);
    fflush(stdout);
    scanf("%s", t);
    if (t[0] == 'Y')
      ans[i] = 'D', curx--;
    else
      ans[i] = 'R', cury--;
  }
  curx = cury = 1;
  for (int i = 2; i <= n; ++i) {
    printf("? %d %d %d %d\n", curx, cury + 1, n, n);
    fflush(stdout);
    scanf("%s", t);
    if (t[0] == 'Y')
      ans[i] = 'R', cury++;
    else
      ans[i] = 'D', curx++;
  }
  printf("! %s\n", ans + 2);
  return 0;
}
