“…If the elements of vectors are negative, we can transform negative elements to positive elements, then perform scalar product of positive elements. For example, we would like to compute the scalar product of two vectors ( 2,3,6,7) − − and (4, 5,2, 6) − − in 15 Z , we can firstly transform them to (13,3,9,7) and (4,10,2,9) , then compute (…”