unsigned long Factorial(unsigned short n)
{
    unsigned long result=n;
    while(--n)
        result*=n;
    return result;
}

//m中选n个的排列组合Amn
int functionA(int m,int n)
{
    int sum=1;
    for(int i=m;i>=m-n+1;i--)
    {
        sum*=i;
    }
    return sum;
}
//n的阶乘
int functionB(int m)
{
    int sum=1;
    while(m>=1)
    {
        sum*=m;
        m--;
    }
    return sum;
}

//Cmn
int functionC(int m,int n)
{
    return functionB(m)/functionB(n)/functionB(m-n);
}