a={}for k=1,12 do a[k]=io.read("*n")end for z=1,9 do a[z]=a[z]-a[10+~-z%3]end s=0 for z=1,3 do q=-~z%3;s=s+a[z]*(a[7+z%3]*a[4+q]-a[4+z%3]*a[7+q])end print(math.ceil(s/6))