def fx(M,N,P):
    if M<N: M,N=N,M
    if M==1:    return P
    if N==1:    return 2*P**2+(M-2)*P**3
    return      4*P**3+2*(N-2+M-2)*P**4+(N-2)*(M-2)*P**5

def main():
    M,N=map(int,input().split())
    P=float(input())
    print(fx(M,N,P))

main()