(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;
}