What Does CRASH mean?

and why is there WA on 7 test?

double res = 1;
            int i = 0, k = 0;
            k = n / q;
            while (i < k)
            {
                res = res * (n - i * q);
                i++;
            }
            if(n % q != 0)
            {
                res = res * (n % q);
            }
            return res;

anu chaiciklao ra mec magas miwers rekursiit vwerdi :/ :(