class Solution {
    public int countElements(int[] arr) {
        int counter = 0;
        Arrays.sort(arr);
        int tmp =1;
        for (int i = 1; i <arr.length; i++) {
            if(arr[i]==arr[i-1]) {
                tmp++;
                continue;
            }
            if(arr[i]==arr[i-1]+1){
                counter+=tmp;
                tmp=1;
            }
            tmp=1;
        }
        return counter;
    }
}