class Solution {
    public int countPairs(int[] nums, int k) {
        List<Integer>[] seen = new List[101];
        int n = nums.length, count = 0;
        for (int i = 0; i < 101; i++)
            seen[i] = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            for (int j : seen[nums[i]])
                if ((i * j) % k == 0)
                    count++;
            seen[nums[i]].add(i);
        }
        return count;
    }
}