20-21_N2

def dig(l):
    if ord(l) >= ord('A') and ord(l) <= ord('F'):
        return 10 + ord(l) - ord('A')
    return ord(l) - ord('0')

def from_16(s):
    ar = []
    for i in s:
        ar.append(dig(i))
    ar = ar[::-1]
    tot = 0
    for i in range(len(s)):
        tot += (16**i) * ar[i]
    return tot


def xor(a, b):
    return a ^ b

def shift(x):
    s = bin(x)
    t = s[len(s) - 1] + s[:len(s) - 1]
    t = t[3:]
    res = int(t, 2)
    return res

def K_shift(x, K):
    for i in range(K):
        x = shift(K)
    return x

def f(a, b, K):
    a = from_16(a)
    b = from_16(b)
    res =  xor(a,b)
    res = K_shift(res, K)
    return res
a = '1A2B'
b = 'FFFF'
K = 4
must = from_16('4E5D')

print(f(a,b, K), must)