import numpy as np
p, q, r, K = map(int, input().split())
mat = np.array([[1, 1, 1], [1, 0, 0], [0, 1, 0]], dtype=np.int32)
ans = np.array(np.eye(3), dtype=np.int32)
K -= 3
while K > 0:
    if K & 1:
        ans = np.dot(mat, ans)
    mat = np.dot(mat, mat)

    for i in range(3):
        for j in range(3):
            ans[i][j] %= 10
            mat[i][j] %= 10
    K >>= 1

x = ans[0][0]*r+ans[0][1]*q+ans[0][2]*p
print(x % 10)