import random
from math import gcd

def pfact(m):
	pf = {}
	for i in range(2,int(m**0.5)+1):
		while m%i == 0:
			pf[i] = pf.get(i,0) + 1
			m //= i
	if m>1 : pf[m]=1
	return pf


def euler(m):
	#pfactのdefが必須
	tmp = pfact(m)
	ans = 1
	for i, j in tmp.items():
		ans = ans * (i**(j-1)) * (i-1)
	return ans


while True:
	"""
	m = random.randrange(0, 10)
	d = random.randrange(0, 10)
	n = random.randrange(0, 1000)
	b = random.randrange(2, 12)
	"""
	m = int(input())
	d = int(input())
	n = int(input())
	b = int(input())
	"""
	m = 9
	d = 3
	n = 82
	b = 9
	"""
	def fast(m,d,n,b):
		nb = b * euler(b) // gcd(b, euler(b))
		v = [[0] * nb for i in range(61)]
		for i in range(nb):
			if (i+d)%nb != 0:
				v[0][i] = pow(i+d, i, nb)
			else:
				v[0][i] = 0

		for i in range(60):
			for j in range(nb):
				v[i+1][j] = v[i][v[i][j]]

		if n == 0:
			r = '0123456789ABCDEFG'
			return r[m % nb]

		if m == 0 and d == 0:
			n -= 1
			m = 1

		m %= nb
		for i in range(61):
			if (n >> i) & 1:
				m = v[i][m]

		r = '0123456789ABCDEFG'
		return r[m % b]

	def naive(m,d,n,b):
		if n == 0:
			r = '0123456789ABCDEFG'
			return r[m % b]
		if m == 0:
			n -= 1
			if d == 0:
				m = 1
			else:
				if (m+d)%b == 0:
					m = 0
				else:
					m = pow(m+d, m, b)
		m %= b
		for i in range(n):
			if (m+d)%b != 0:
				m = pow(m+d, m, b)
			else:
				m = 0
		
		r = '0123456789ABCDEFG'

		return r[m]

	#if fast(m,d,n,b) != naive(m,d,n,b):
	#	print(m,d,n,b)
	#	print(fast(m,d,n,b), naive(m,d,n,b))
	#	break
	print(fast(m,d,n,b))
	break