number_of_divisors

int F(int n) {
    set<int> ans;
    for (int i = 2; i <= n; i++) {
        if (n % i == 0) {
            ans.insert(i);
            while (n % i == 0)
                n /= i;
            i = 2;
        }
    }
    return ans.size();
}