def closestNumbers(arr):
    # Write your code 
    arr.sort()
    result = {}
    for index in range(len(arr)):
        if (index +1 < len(arr)):
            current_dif = abs(arr[index] - arr[index + 1])
            if (current_dif in result):
                result[current_dif].append((arr[index], arr[index + 1]))
            else:
                result[current_dif] = [(arr[index], arr[index + 1])]
    
    min_key = min(list(result.keys()))
    arr_result = result[min_key]
    final_result = []
    for item in arr_result:
        final_result.extend(item)
    return final_result