import sys

sys.setrecursionlimit(10 ** 6)
from bisect import *
from collections import *
from heapq import *

def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def SI(): return sys.stdin.readline()[:-1]
def LLI(rows_number): return [LI() for _ in range(rows_number)]
int1 = lambda x: int(x) - 1
def MI1(): return map(int1, sys.stdin.readline().split())
def LI1(): return list(map(int1, sys.stdin.readline().split()))
p2D = lambda x: print(*x, sep="\n")
dij = [(1, 0), (0, 1), (-1, 0), (0, -1)]

def main():
    # 0まだ 1済み
    m = [[0] * 60 for _ in range(60)]
    i = j = 30
    m[i][j]=1
    d = 0
    log = []

    def check(ret):
        if ret == "0":
            di, dj = dij[d]
            m[i + di][j + dj] = 1
        while ret == "20151224":
            print("F", flush=True)
            ret = input()
        if ret == "Merry Christmas!":
            exit()

    def F(i, j):
        print("F", flush=True)
        ret = input()
        check(ret)
        di, dj = dij[d]
        i, j = i + di, j + dj
        m[i][j] = 1
        return ret,i,j

    def B(i, j):
        print("B", flush=True)
        ret = input()
        check(ret)
        di, dj = dij[d]
        i, j = i - di, j - dj
        return ret,i,j

    def R(d):
        print("R", flush=True)
        ret = input()
        check(ret)
        d = (d - 1) % 4
        return ret, d

    def L(d):
        print("L", flush=True)
        ret = input()
        check(ret)
        d = (d + 1) % 4
        return ret, d

    ret = input()
    check(ret)
    while 1:
        # 直進できるだけする
        di,dj=dij[d]
        while ret != "0" and m[i+di][j+dj]==0:
            ret, i, j = F(i, j)
            log.append(0)
        # まだ行っていなければ右を向く
        di, dj = dij[(d - 1) % 4]
        if m[i + di][j + dj] == 0:
            ret, d = R(d)
            log.append(-1)
            continue
        # 右がダメなら左
        di, dj = dij[(d + 1) % 4]
        if m[i + di][j + dj] == 0:
            ret, d = L(d)
            log.append(1)
            continue
        # それもだめなら戻る
        noback=True
        while log[-1]!=0 or noback:
            dir=log.pop()
            if dir==1:ret,d=R(d)
            elif dir==-1:ret,d=L(d)
            else:
                ret, i, j = B(i, j)
                noback=False

main()