import sys

sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline
f_inf = float('inf')
MOD = 10 ** 9 + 7


def solve():
    p, q, r, k = map(int, input().split())
    p, q, r = map(lambda x: x % 10, [p, q, r])
    MAX = 1001
    dp = [0] * MAX
    dp[0], dp[1], dp[2] = p, q, r
    cycle = 0
    for i in range(3, MAX):
        cycle += 1
        dp[i] = (dp[i - 3] + dp[i - 2] + dp[i - 1]) % 10
        if (dp[0], dp[1], dp[2]) == (dp[i - 2], dp[i - 1], dp[i]):
            break
    k %= cycle
    print(dp[k - 1])


if __name__ == '__main__':
    solve()