def make_valley(arr):
    # your code
    arr.sort()
    arr.reverse()
    l = []
    r = []
    x = len(arr)
    arr1 = []
    for i in range(x):
        if i % 2 == 0:
            l.append(arr[i])
        elif i % 2 == 1:
            r.append(arr[i])
    r.reverse()
    arr1 = l + r
    return arr1


def make_valley2(arr):
    arr = sorted(arr, reverse=True)
    return arr[::2] + arr[1::2][::-1]
