public Integer seekArr(int [] arr){
        if(arr == null || arr.length < 1 || arr.length % 2 == 0){
            return null;
        }
        int arrLength = arr.length;
        if(arrLength == 1 || arr[0] != arr[1]){
            return arr[0];
        }
        if(arr[arrLength - 1] != arr[arrLength - 2]){
            return arr[arrLength - 1];
        }
        return seek(0, arrLength - 1, arr);
    }