Problem of Euler

[Lain]

Hi All!
You are given 8 numbers:a, b, c, d, e, f, g, h and you should find A, B, C, D such that holds:
( a^2 + b^2 + c^2 + d^2 ) ( e^2 + f^2 + g^2 + h^2 ) = ( A^2 + B^2 + C^2 + D^2 )


How to solve it?

Full desc:
http://acm.zju.edu.cn/SAMS/marriage/marriage.htm

Thanks.