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 C (judge verdict: Accepted)

#include<stdio.h>


int sum[100000],i;

int num(int r,int l)
{
    int x,y,z,w;
    x=sum[l];
    y=r-1;
    for(z=r;z<l;z++)
    {
        if(sum[z]<=x)
        {
            y++;
            w=sum[y];sum[y]=sum[z];sum[z]=w;
        }
    }
    w=sum[y+1];sum[y+1]=sum[l];sum[l]=w;
    return y+1;
}
int main()
{
    int a,b;
    scanf("%d",&i);
    for(a=0;a<i;a++)
    {
        scanf("%d",&sum[a]);
        
    }
    b=num(0,i-1);
    for(a=0;a<i;a++)
    {
        if(a)printf(" ");
        if(a==b)printf("[");
        printf("%d",sum[a]);
        if(a==b)printf("]");
    
    }
    printf("\n");
    return 0;
    
}