P, Q, R, K = map(int, input().split())
PQR = P % 10 * 100 + Q % 10 * 10 + R % 10
K -= 3
Next = [[0] * 1000 for _ in range(64)]

for i in range(1000):
    Next[0][i] = i * 10 % 1000 + (i // 100 % 10 + i // 10 % 10 + i % 10) % 10

for i in range(63):
    for j in range(1000):
        Next[i + 1][j] = Next[i][Next[i][j]]

for i in range(64):
    if K >> i & 1: PQR = Next[i][PQR]
print(PQR % 10)