n, m = map(int, input().split())
p = float(input())

if n == 1:
    if m == 1:
        ans = p
    else:
        ans = 2*p*p+(m-2)*p*p**2
else:
    if m == 1:
        ans = 2*p*p+(n-2)*p*p**2
    else:
        ans = 4*p*p**2+(2*(m-2)+2*(n-2))*p*p**3+(m-2)*(n-2)*p*p**4
print(ans)