Problem: You are given a set $T$, which is a subset of $S$. The set $S$ consists of $0, 1, ... n-1$. Print all subsets of $T$. Note that we represent $0, 1, ... n-1$ as 00...0001, 00...0010, 00...0100, ..., 10...0000 in binary respectively and the integer representation of a subset is calculated by bitwise OR of existing elements.

Constraints

* $1 \leq n \leq 28$
* $0 \leq k \leq 18$
* $k \leq n$
* $0 \leq b_i < n$

Input

The input is given in the following format.


$n$
$k \; b_0 \; b_1 \; ... \; b_{k-1}$


$k$ is the number of elements in $T$, and $b_i$ represents elements in $T$.

Output

Print the subsets ordered by their decimal integers. Print a subset in the following format.


$d$: $e_0$ $e_1$ ...


Print ':' after the integer value $d$, then print elements $e_i$ in the subset in ascending order. Separate two adjacency elements by a space character.

Example

Input

4
2 0 2


Output

0:
1: 0
4: 2
5: 0 2

Solution (in CPP):

Solution:
#include <iostream>
#include<list>
#include<vector>
#include<stack>
#include<queue>
#include<algorithm>
#include<set>
#include<map>
#include<bitset>
using namespace std;

int main()
{
    unsigned long n,q,k,all;
    bitset<30> a(0),b(0);
    cin>>n;
    all=1<<n;
    cin>>n;
    while(n--){
        cin>>q;
        b.set(q,1);
    }
    for(int i=0;i<all;i++){
        a=i;
        if((a|b)==b){
            cout<<i<<":";
            for(int i=0;i<30;i++){
                if(a.test(i)){
                    cout<<" "<<i;
                }
            }
            cout<<"\n";
        }
    }

}