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 <iomanip>
#include<vector>
#include <algorithm>
#include <queue>
#include<string>
#include <map>
#include <cmath>
#include <deque>
#include <list>
#include <stack>
#include <queue>
#include <utility>
#include <set>
#include <bitset>
typedef long long ll;
typedef long double ld;

#define REP(i,s,n)for(ll i=s;i<(n);++i)
#define rep(i,n) REP(i,0,n)
using namespace std;


int main() {
	ll N,K;
	cin >> N>>K;
	vector<ll>A(N);
	rep(i,N) {
		A[i] = i;
	}
	ll B=0;
	rep(i, K) {
		ll b;
		cin >> b;
		B |= (1 << b);
	}

	for (int i = 0; i < (1 << N); ++i) {
		if ((i&(~B)) == 0) {
			vector<ll>C;
			for (int j = 0; j < N; ++j) {
				if ((i&(1 << j))) {
					C.push_back(A[j]);
				}
			}
			cout << i << ":";
			for (int j = 0; j < C.size(); ++j) {
				cout << " " << C[j];
			}
			cout << endl;
		}
	}
	return 0;
}