下面函数的功能是计算s=1+1/(1*2)+1/(1*2*3)+...+1/(1*2*3*...*n)，请填空。 double+fun(int+n) { +____+s=0.0,fac=1.0

double fun(int n)
{
    double s = 0.0, fac = 1.0;
    for (int i = 1; i <= n; i++)
    {
        fac *= i;
        s += 1 / fac;
    }
    return s;
}