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

A = {}
A[0] = p % 10
A[1] = q % 10
A[2] = r % 10

def conv(a, b, c):
    return (a % 10) * 100 + (b % 10) * 10 + c % 10

for k in range(3, 2000):
    A[k] = (A[k - 1] + A[k - 2] + A[k - 3]) % 10

if K - 1 < 2000:
    print(A[K - 1])
    exit()

d = {}
for k in range(2, 2000):
    x = conv(A[k], A[k - 1], A[k - 2])
    if x in d:
        loop_start = d[x]
        loop_len = k - loop_start
        break
    d[x] = k

n = ((K - 1) - loop_start) % loop_len + loop_start
print(A[n])