def closestNumbers(arr):
    arr.sort()
    mindif = arr[-1] - arr[0]
    results = []
    
    for i in range(len(arr) - 1):
        diff = arr[i + 1] - arr[i]
        if diff < mindif:
            mindif = diff + 0
            results = [arr[i], arr[i + 1]]
        elif diff == mindif:
            results.append(arr[i])
            results.append(arr[i + 1])
    
    return results