#include <bits/stdc++.h>
using namespace std;
void getint(int &v) {
  char ch, fu = 0;
  for (ch = '*'; (ch < '0' || ch > '9') && ch != '-'; ch = getchar())
    ;
  if (ch == '-') fu = 1, ch = getchar();
  for (v = 0; ch >= '0' && ch <= '9'; ch = getchar()) v = v * 10 + ch - '0';
  if (fu) v = -v;
}
int n, x, y, ts, top;
char s[555], tmp[555555], stk[555555];
bool ck(int a, int b, int c, int d) {
  printf("? %d %d %d %d\n", a, b, c, d);
  fflush(stdout);
  scanf("%s", s);
  if (s[0] == 'Y')
    return 1;
  else
    return 0;
}
int main() {
  cin >> n;
  x = y = 1;
  for (int i = 1; i <= n - 1; i++) {
    if (ck(x, y + 1, n, n))
      ++y, tmp[++ts] = 'R';
    else
      ++x, tmp[++ts] = 'D';
  }
  x = y = n;
  for (int i = 1; i <= n - 1; i++) {
    if (ck(1, 1, x - 1, y))
      --x, stk[++top] = 'D';
    else
      --y, stk[++top] = 'R';
  }
  printf("! ");
  for (int i = 1; i <= ts; i++) putchar(tmp[i]);
  for (int i = top; i >= 1; i--) putchar(stk[i]);
  puts("");
  return 0;
}
