unsigned long fun(unsigned long n)
{
    unsigned long x = 0; int t;
    while (n)
    {
        t = n % 10;
        /********** found **********/
        if (t % 2 == _______)
            /********** found **********/
            x = _____ + t;
        /********** found **********/
        n = _______;
     }
     return x;
}