n,m=map(int,input().split())
p=float(input())
if n==1 and m==1:
    print(1-p)
elif min(n,m)-1:
    print(2 * ((1-p)**2) + (max(n,m)-2) * ((1-p)**3))
else:
    print(4 * ((1-p)**3) + (n+n+m+m-8) * ((1-p)**4) + (n*m-(n+n+m+m-4))*((1-p)**4))