M = int(input())
D = int(input())
N = int(input())
B = int(input())

if N == 0:
    result = M % B
    print('A' if result == 10 else result)
    exit()

D_mod = D % B
m0 = M % B

f = [0] * B
for m in range(B):
    if m == 0:
        f[m] = 1 % B
    else:
        base = (m + D_mod) % B
        exponent = m
        f[m] = pow(base, exponent, B)

prev_states = {}
steps = []
current = m0

while True:
    if current in prev_states:
        start_step = prev_states[current]
        cycle = steps[start_step:]
        cycle_length = len(cycle)
        if N < len(steps):
            result = steps[N]
        else:
            remaining = N - start_step
            pos = remaining % cycle_length
            result = cycle[pos]
        break
    else:
        prev_states[current] = len(steps)
        steps.append(current)
        current = f[current]

if result == 10:
    print('A')
else:
    print(result)