code: private static final void sqrt(long10 x, long10 u) {
  		long10 v=new long10(), t1=new long10(), t2=new long10();
  		add(t1, u, u);	/* t1 = 2u		*/
  		recip(v, t1, 1);	/* v = (2u)^((p-5)/8)	*/
  		sqr(x, v);		/* x = v^2		*/
  		mul(t2, t1, x);	/* t2 = 2uv^2		*/
  		t2._0--;		/* t2 = 2uv^2-1		*/
  		mul(t1, v, t2);	/* t1 = v(2uv^2-1)	*/
  		mul(x, u, t1);	/* x = uv(2uv^2-1)	*/
  	}
docs: /* a square root