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

int main() {
	int n, k, b;
	cin >> n >> k;

	vector<int> t(k);
	for (int i = 0; i < k; i++)  cin >> t[i];
	sort(t.begin(), t.end());

	for (int i = 0; i < 1 << k; i++) {
		int d = 0;
		vector<int> temp;
		for (int j = 0; j < k; j++) {
			if (i & 1 << j) {
				d |= 1 << t[j];
				temp.push_back(t[j]);
			}
		}
		cout << d << ":";
		for (int j : temp)    cout << " " << j;
		cout << endl;
	}

	return 0;
}