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

ans = 0
if n == 1 and m == 1:
    print(p)
    exit()
if (n == 1 and m != 1) or (n != 1 and m == 1):
    e = max(n, m)
    print(2 * p**2 + (e - 2) * p**3)
    exit()

print(4 * p**3 + 2 * (m + n - 4) * p**4 + (m - 2) * (n - 2) * p**5)