N, M = map(int, input().split())
P = float(input())

x_corner = 3
if M == 1: x_corner -= 1
if N == 1: x_corner -= 1
x_ud = 4
if N < 2: x_ud -= 1
x_lr = 4
if M < 2: x_lr -= 1
x_inner = 5

corner = 4
if N == M == 1: corner = 1
if N == 1 or M == 1: corner = 2
ud = max(0, 2 * (M - 2))
lr = max(0, 2 * (N - 2))
inner = max(0, M - 2) * max(0, N - 2)

ans = corner * P**x_corner + ud * P**x_ud + lr * P**x_lr + inner * P**x_inner
print(ans)