from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.buffer.readline

N,M = map(int,input().split())
P = float(input())
ans = 0
N,M = min(N,M),max(N,M)
if N==1:
    if M==1:
        print(P)
    else:
        ans = 2*P + (M-2)*P**2
        ans *= P
        print(ans)
    exit()
ans += 4*P**2
ans += 2*(N+M-4)*P**3
ans += (N-2)*(M-2)*P**4
ans *= P
print(ans)