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

if N==1:
    print(2*P**2+(M-2)*P**3)
elif M==1:
    print(2*P**2+(N-2)*P**3)
else:
    print(4*P**3+2*(N+M-4)*P**4+(N-2)*(M-2)*P**5)