def back_c(r):
    rt = [18, 30, 42, 43, 44, 32, 20, 19]
    rotate(r, rt)
    L = [0, 3, 6, 9, 21, 33, 45, 48, 51, 15, 27, 39]
    return shift(r, L)
def back_c(r):
    rt = [18, 30, 42, 43, 44, 32, 20, 19]
    rotate(r, rt)
    L = [0, 3, 6, 9, 21, 33, 45, 48, 51, 15, 27, 39]
    return shift(r, L)