import sys

N = 50
flush = sys.stdout.flush

used = [[0]*N for i in xrange(N)]
dx = [-1, 0, 1, 0]
dy = [0, -1, 0, 1]

# (x, y, dir)
st = [[0, 0, 0, 4]]
used[0][0] = 1
while 1:
    s = raw_input()
    if s[0]=="M": exit(0)
    d = int(s)
    if d == 20151124:
        print"F"
        flush()
        continue
    x, y, di, f = el = st[-1]
    nx = x + dx[di]; ny = y + dy[di]
    if d and not used[ny][nx]:
        print"F"; flush()
        st.append([nx, ny, di, 4])
        used[ny][nx] = 1
    else:
        if f==0:
            print "B"; flush()
            st.pop()
        else:
            el[2] = (di + 1) % 4
            el[3] = f-1
            print"R"; flush()