A = list(map(int,input().split())) B = list(map(int,input().split())) if (min(A[2],B[2])-max(A[0],B[0])) < 0 or (min(A[1],B[1])-max(A[3],B[3])) < 0: print(0) else: print((min(A[2],B[2])-max(A[0],B[0]))*(min(A[1],B[1])-max(A[3],B[3])))