N, M = map(int, input().split())
P = float(input())
if N >= M:
    N, M = M, N
ans = 0
if N == 1:
    if M == 1:
        ans = P
    else:
        ans = 2 * P ** 2 + max(0, M - 2) * P ** 3
else:
    ans = 4 * P ** 3 + 2 * (N + M - 4) * P ** 4 + (M - 2) * (N - 2) * P ** 5
print(ans)