n, m = map(int, input().split())
p = float(input())
if m < n:
    n, m = m, n
if n == m == 1:
    print(p)
elif n == 1:
    ans = 2 * p ** 2
    ans += (m - 2) * p ** 3
    print(ans)
else:
    ans = 4 * p ** 3
    ans += 2 * (n - 2 + m - 2) * p ** 4
    ans += (n - 2) * (m - 2) * p ** 5
    print(ans)