实验描述：给定X和Y都是n位整数，计算乘积XY。分治算法思想，将n位X和Y分成2段，每段n/2位。则X分为AB两段，Y分为CD两段。

有X=A*(10)^(n/2)+B，Y=C*(10)^(n/2)+D；XY=(A*(10)^(n/2)+B)(C*(10)^(n/2)+D)=AC*(10)^n+(AD+BC)*(10)^(n/2)+BD。 -Experiment: given X and Y are n-bit integers, calculate the product of the XY. The idea of ​ ​ divide and conquer algorithm, the n-bit X and Y is divided into two segments, each n/2. Then X is divided into AB two Y divided into CD two. X = A* (10) ^ (n/2)+B, Y, = C* (10) ^ (n/2)+D　the XY = (A* (10) ^ (n/2)+B) (C* (10) ^ (n/2)+D) = AC* (10) ^ n+ (AD+BC)* (10) ^ (n/2)+BD.