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 <algorithm>
#include <vector>

int main()
{	
	int n; std::cin >> n;
	int k; std::cin >> k;
	int* T = new int[k];
	for (int i=0; i<k; i++) std::cin >> T[i];
	std::sort(T, T+k);

	for (long long int i=0; i<(1<<k); i++) {
		long long index = 0;
		std::vector<int> output;
		long long d = i;
		for (int j=0; j<k; j++) {
			if ( (d&1) == 1 ) {
				index += 1<<T[j];
				output.push_back(T[j]);
			}
			d >>= 1;
		}
		std::cout << index << ":";
		for (std::vector<int>::iterator it = output.begin(); it != output.end(); ++it) std::cout << " " << *it;
		std::cout << std::endl;
	}
	
	delete[] T;
	
	return 0;
}