一些技巧

\(gcd(x,y,z)=gcd(x,y-x,z-y)\)
对于\([x,y]\),\((x,y)\)之类的题目，应该将\([x,y]→[x,y]\),\((x,y)→[x-0.5,y+0.5]\)
\(0!=1\)
\(C(n,m)=C^{m}_{n}=\frac{n!}{m!\ast(n-m)!}\)
矩阵快速幂的\(ans\)要设为初始矩阵
莫队\(l=r=1,add(1)\)
阶段、状态、决策
\(exgcd\)的板子

int exgcd(int a, int b, int &x, int &y) {
	if (!b) {x = 1, y = 0; return a;}
	int gcd = exgcd(b, a % b, x, y);
	int z = x; x = y, y = z - (a / b) * y;
	return gcd; 	
}