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

if N==1 and M==1:
    print(P)
elif N==1 or M==1:
    ans += (max(0,N-2)+max(0,M-2))*P**3
    ans += 2*P**2
    print(ans)
else:
    ans = max(0,N-2)*max(0,M-2)*P**5
    ans += (2*max(0,N-2)+2*max(0,M-2))*P**4
    ans += 4*P**3
    print(ans)