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

ANS=0

if N==1:
    for j in range(M):
        if j==0 or j==M-1:
            ANS+=P**2
        else:
            ANS+=P**3

elif M==1:
    for i in range(N):
        if i==0 or i==N-1:
            ANS+=P**2
        else:
            ANS+=P**3

else:
    for i in range(N):
        for j in range(M): 
            if (i==0 or i==N-1) and (j==0 or j==M-1):
                ANS+=P**3

            elif i==0 or j==0 or i==N-1 or j==M-1:
                ANS+=P**4

            else:
                ANS+=P**5

print(ANS)