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

ANS=0
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)