# 行列掛け算
def matmul(a,b):
	c = [[0]*len(b[0]) for _ in range(len(a))]
	for i in range(len(a)):
		for j in range(len(b[0])):
			for k in range(len(b)):
				c[i][j] += a[i][k]*b[k][j]
				c[i][j] %= 10
	return c

# 行列累乗
def matpow(a,n):
	b = [[0]*len(a) for _ in range(len(a))]
	for i in range(len(a)):
		b[i][i] = 1
	while n>0:
		if n&1: b = matmul(b,a)
		a = matmul(a,a)
		n >>= 1
	return b


p,q,r,k = map(int,input().split())
mat = [[1,1,1],[1,2,2],[2,3,4]]
mk = matpow(mat,(k-1)//3)
print((mk[(k-1)%3][0]*p+mk[(k-1)%3][1]*q+mk[(k-1)%3][2]*r)%10)