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<bitset>
#include<vector>
using namespace std;

int main(){

    bitset<28> subset, T;
    
    int n, k, b;
    cin >> n >> k;
    while (k--){
        cin >> b;
        T[b] = 1;
    }

    for(int i = 0; i < (1 << n); i++){
        subset = i;
        if((subset & T) == subset){
            cout << i << ":";            
            for(int j = 0; j < n; j++){
                if(subset[j]){
                    cout << ' ' <<  j;
                }
            }
            cout << endl;            
        }

    }
    return 0;
}