# 周期、サイクル

from collections import defaultdict

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

A = [-1] * 10 ** 5
A[0] = p % 10
A[1] = q % 10
A[2] = r % 10

# ３点が一致すれば循環する
visited = defaultdict(tuple)
steps = [(-1, -1, A[0]), (-1, -1, A[1]), (-1, -1, A[2])]

pos = (A[0], A[1], A[2])
cnt = 2
while pos not in visited:
    visited[pos] = 1
    steps.append(pos)
    cnt += 1
    A[cnt] = A[cnt - 1] + A[cnt - 2] + A[cnt - 3]
    A[cnt] %= 10
    pos = (A[cnt - 2], A[cnt - 1], A[cnt])
    if cnt == K - 1:
        print(A[K - 1])
        exit()

# print(steps)

loop_start = steps.index(pos)  # ループの開始点
loop_cycle = len(steps) - loop_start  # ループの周期

# print(loop_start, loop_cycle)

freq, pos = divmod(K - loop_start - 1, loop_cycle)  # freq:周回数、pos:到着位置
# ans = steps[loop_start + pos] + 1
ans = steps[loop_start + pos]

print(sum(ans) % 10)