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>
using namespace std;

int main(){
	int n, k, b, T = 0;
	
	cin>>n;
	
	cin>>k;
	
	for(int i = 0; i < k; i++){
		cin>>b;
		T |= 1<<b;
	}
	
	for(int i = 0; i < (1<<n); i++){
		if((~T)&i) continue;
		cout<<i<<":";
		for(int j = 0, k = i; k; j++){
			if(k&(1<<j)){
				cout<<" "<<j;
				k &= ~(1<<j);
			}
		}
		cout<<endl;
	}
	
	return 0;
}