def matrixmul(A, B):
    C = [[0] * 3 for _ in range(3)]
    for i, row in enumerate(A):
        Ci = C[i]
        for j, vA in enumerate(row):
            for k, vB in enumerate(B[j]):
                Ci[k] = (Ci[k] + vA * vB) % 10
    return C

def matrixpow(A, e):
    R = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
    while e > 0:
        if e & 1:
            R = matrixmul(R, A)
        e >>= 1
        A = matrixmul(A, A)
    return R

p, q, r, K = map(int, input().split())
A = [[1, 1, 1], [1, 0, 0], [0, 1, 0]]
init = [[r % 10], [q % 10], [p % 10]]
B = matrixmul(matrixpow(A, K - 3), init)
print(B[0][0])