m = int(input())
d = int(input())
n = int(input())
b = int(input())
v = [[0] * b for i in range(60)]
for i in range(b):
	if (i+d)%b != 0:
		v[0][i] = pow(i+d, i, b)
	else:
		v[0][i] = 0

for i in range(59):
	for j in range(b):
		v[i+1][j] = v[i][v[i][j]]

m %= b
if n == 0 and m == 0 and d == 0:
	print(0)
	exit()

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

for i in range(60):
	if (n >> i) & 1:
		m = v[i][m]

r = '0123456789ABCDEFG'

print(r[m])