import sys
import numpy as np
# sys.setrecursionlimit(10 ** 9)  # Codeforcesでは350000程度に
def input(): return sys.stdin.readline().strip()


p, q, r, k = map(int, input().split())


mod = 10


def mat_mul(A, B, mod=mod):
    A1, A2 = A >> 15, A & (1 << 15) - 1
    B1, B2 = B >> 15, B & (1 << 15) - 1
    X = (A1 @ B1) % mod
    Y = (A2 @ B2) % mod
    Z = ((A1 + A2) @ (B1 + B2) - X - Y) % mod
    return ((X << 30) + (Z << 15) + Y) % mod


A = np.array([[r % mod], [q % mod], [p % mod]])
M = np.array([[1, 1, 1], [1, 0, 0], [0, 1, 0]])
k -= 3
while k > 0:
    if k % 2 == 1:
        A = mat_mul(M, A)
    M = mat_mul(M, M)
    k //= 2

print(A[0][0] % mod)