N,M = map(int,input().split())
p = float(input())
ans = 0
#1マスのとき
if N == 1 and M == 1:
    print(p)
    exit()
#細長いとき
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()
#それ以外
print(4* p**3 + 2*(M+N-4)* p**4 + (M-2)*(N-2)* p**5 )