int myMulti(unsigned long *a, int len_a, unsigned long *c)
{
	int i=0, j=0;
	unsigned long step=0;
	__int64 h=0;
	unsigned long *p_h=(unsigned long *)&h;
	memset(c, 0, sizeof(unsigned long)*(len_a<<1));
	for(i=0; i<len_a; i++)
	{
		step=0;
		h=(__int64)a[i]*a[i]+c[i<<1]+step;
		unsigned long temp=(p_h[0]>>base);
		step=(p_h[1]<<(32-base))+temp;
		c[i<<1]=(p_h[0]-(temp<<base));   
				
		for(j=i+1; j<len_a; j++)
		{
			h=(__int64)a[i]*(a[j]<<1)+c[i+j]+step;
			temp=(p_h[0]>>base);
			step=(p_h[1]<<(32-base))+temp;
			c[i+j]=(p_h[0]-(temp<<base));
		}
		c[(j++)+i]=step;
	}
	return i+j-1;
}