def Matprod(A, B, mod):
    N = len(A)
    temp = [[0] * N for i in range(N)]
    for i in range(N):
        for j in range(N):
            for k in range(N):
                temp[i][j] += A[i][k] * B[k][j]
                temp[i][j] %= mod
    return temp

def Matpow(A, M, mod):
    N = len(A)
    Mat = [[0] * N for i in range(N)]
    for i in range(N):
        Mat[i][i] = 1
         
    for i in range(64):
        if (M >> i) & 1:
            Mat = Matprod(Mat, A, mod)
        A = Matprod(A, A, mod)
    return Mat     

p, q, r, K = map(int, input().split())
A = [[1, 1, 1], [1, 0, 0], [0, 1, 0]]
A = Matpow(A, K - 3, 10)
ans = A[0][0] * r + A[0][1] * q + A[0][2] * p
ans %= 10
print(ans)