基本模运算

1.概念：模运算是指取模运算，即求m/n的余数。模运算有许多基本规则，熟练掌握可以更好的编程。

2.交换律：

                        (a + b) % m = (b + a) % m

                        (a * b) % m = (b * a) % m

3.结合律：

                        [(a+b)%m+c]%m = [a+(b+c)%m]%m

                        [(a*b)%m*c]%m = [(b*c)%m*a]%m

4.分配律：

                        [(a+b)%m * c] % m = [(a*c)%m + (b*c)%m] % m

                        (a+b)%m = (a%m + b%m)%m

                        (a - b)%m = (a%m - b%m)%m

                        (a*b)%m = (a%m * b%m)%m

                        a^b % m = (a%m)^b % m
5.重要结论：