N,M = map(int,input().split())
P = float(input())
ans = 0

import sys
if N > 1 and M > 1:
    ans += P ** 5 * (N - 2) * (M - 2)
    ans += P ** 4 * (N + M - 4) * 2
    ans += P ** 3 * 4
    print(ans)
    exit()
if N == 1 and M == 1:
    print(P)
    exit()
else:
    if M == 1:
        N,M = M,N
    ans += P ** 3 * (M - 2)
    ans += P ** 2 * 2
    print(ans)