Problem:
Partition

Quick sort is based on the Divide-and-conquer approach. In QuickSort(A, p, r), first, a procedure Partition(A, p, r) divides an array A[p..r] into two subarrays A[p..q-1] and A[q+1..r] such that each element of A[p..q-1] is less than or equal to A[q], which is, inturn, less than or equal to each element of A[q+1..r]. It also computes the index q.

In the conquer processes, the two subarrays A[p..q-1] and A[q+1..r] are sorted by recursive calls of QuickSort(A, p, q-1) and QuickSort(A, q+1, r).

Your task is to read a sequence A and perform the Partition based on the following pseudocode:

Partition(A, p, r)
1 x = A[r]
2 i = p-1
3 for j = p to r-1
4 do if A[j] <= x
5 then i = i+1
6 exchange A[i] and A[j]
7 exchange A[i+1] and A[r]
8 return i+1

Note that, in this algorithm, Partition always selects an element A[r] as a pivot element around which to partition the array A[p..r].

Input

The first line of the input includes an integer n, the number of elements in the sequence A.

In the second line, Ai (i = 1,2,...,n), elements of the sequence are given separated by space characters.

Output

Print the sorted sequence. Two contiguous elements of the sequence should be separated by a space character. The element which is selected as the pivot of the partition should be indicated by [  ].

Constraints

1 ≤ n ≤ 100,000

0 ≤ Ai ≤ 100,000

Sample Input 1

12
13 19 9 5 12 8 7 4 21 2 6 11

Sample Output 1

9 5 8 7 4 2 6 [11] 21 13 19 12

Solution in Python3 (judge verdict: Wrong Answer)

def Partition(A,p,r):
    x = A[r]
    i = p-1
    for j in range(p,r):
        if (A[j] <= x):
            i += 1
            A[i],A[j] = A[j],A[i]
            print("swap:",i,j)
    A[i+1],A[r] = A[r],A[i+1]
    print('swap:',i+1,r)
    return i+1

n = int(input())
st = input()
data = list(map(int,st.split()))

mid = Partition(data,0,len(data)-1)
for i in data:
    print(i)
for i in range(0,mid):
    print(data[i],end=" ")
print("[{0}] ".format(data[mid]),end="")
for i in range(mid+1,len(data)-1):
    print(data[i],end=" ")
print(data[len(data)-1])