#coding: UTF-8

import sys
import re
import itertools
from collections import deque

""" defs """

""" main """
searched_point = list( [0]*50 for _ in range(50) )
dx = [1,0,-1,0]
dy = [0,-1,0,1]

st = [[0,0,0,4]]
searched_point[0][0] = 1

while True:
	s = input()
	if (s[0]=='M'):
		break
	d = int(s)
	if (d==20151224):
		print('F')
		continue

	x,y,drct,f = el = st[-1]
	nx = x + dx[drct]
	ny = y + dy[drct]
	if (d != 0 and searched_point[ny][nx]==False):
		print('F')
		st.append([nx,ny,drct,4])
		searched_point[ny][nx]=1
	else:
		if (f==0):
			print('B')
			st.pop()
		else:
			el[2] = (drct+1) % 4
			el[3] = f-1
			print('L')