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

if N == 1 and M == 1:
    ans = P
elif min(N, M) == 1:
    ans = 2*P**2 + (max(N, M)-2)*P**3
else:
    ans = 4*P**3 + (2*(N+M)-8)*P**4 + (N-2)*(M-2)*P**5
print(ans)