N,M = map(int,input().split())
P = float(input())
if N > M:
    N,M = M,N
ans = 0
P2 = P * P
P3 = P2 * P
P4 = P3 * P
P5 = P4 * P
if N == 1:
    if M == 1:
        print(P)
    else:
        x = M - 2
        ans = 2 * P2
        ans += x * P3
        print(ans)
else:
    x = M - 2
    y = N - 2
    z = N * M - 2 * (x + y) - 4
    ans = 4 * P3
    ans += 2 * (x + y) * P4
    ans += z * P5
    print(ans)