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

#A**n
def mat_pow(A, n, mod):
    B = [[0]*len(A) for i in range(len(A))]
    for i in range(len(A)):
        B[i][i] = 1
    while n > 0:
        if n & 1 == 1:
            B = mat_mul(A, B, mod)
        A = mat_mul(A, A, mod)
        n = n>>1
    return B

p, q, r, K  = map(int, input().split())
mod = 10
X = [r, q, p]
A = [[1, 1, 1], [1, 0, 0], [0, 1, 0]]
A = mat_pow(A, K-3, mod)
ans = 0
for i in range(3):
    ans += A[0][i]*X[i]
print(ans%mod)