组合数快速取模模板

int inv(int a)
{
	return a==1?1:(long long)(MOD-MOD/a)*inv(MOD%a)%MOD;
}
LL C(LL n,LL m)
{
	if(m<0)return 0;
	if(n<m)return 0;
	if(m>n-m)m=n-m;
	LL up=1,down=1;
	for(LL i=0;i<m;i++)
	{
		up=up*(n-i)%MOD;
		down=down*(i+1)%MOD;
	}
	return up*inv(down)%MOD;
}