X={}
x=0
for i=-3,8 do
X[i]=io.read"*n"-(X[i%3-3]or 0)
p=-~i%3
q=~-i%3
x=x+i//6*X[i]*(X[p]*X[q+3]-X[q]*X[p+3])
end
print(x//6)