import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,M = map(int,readline().split())
P = float(read())

def F(N,M,P):
    if N > M:
        N,M = M,N
    A = []
    if N == M == 1:
        A = [(1,P)]
    elif N == 1:
        A.append((2, P**2))
        A.append((M-2, P**3))
    else:
        A.append((4,P**3))
        A.append((N+N+M+M-8,P**4))
        A.append(((N-2)*(M-2),P**5))
    return sum(n * p for n,p in A)

# F(1,2,0.5), F(2,2,0.25), F(1333,79,0.63)

answer = F(N,M,P)
print(answer)