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

current = M % B
steps = 0
prev = None

while steps < N:
    if current == prev:
        # Convergence detected, break the loop
        break
    prev = current
    a = (current + D) % B
    e = current
    if a == 0:
        if e == 0:
            current = 1 % B
        else:
            current = 0
    else:
        if e == 0:
            current = 1 % B
        else:
            current = pow(a, e, B)
    steps += 1

# Determine the last digit in base B
digit = current % B
print(digit if digit < 10 else 'A')