class Solution {
    public boolean uniqueOccurrences(int[] arr) {
        int[] occur=new int[2001];
        
        for(int num:arr){
            occur[1000+num]++;
        }
        
        Arrays.sort(occur);
        for(int i=0; i<occur.length-1; i++){
            if(occur[i]==occur[i+1]&&occur[i]!=0)
                return false;
        }
        
        return true;
    }
}