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:
#define _CRT_SECURE_NO_WARNINGS
#include<bits/stdc++.h>
#define INF         1e9
#define EPS         1e-9
#define REP(i,n)    for(lint i=0,i##_len=(n);i<i##_len;++i)
#define REP1(i,n)   for(lint i=1,i##_len=(n);i<=i##_len;++i)
#define REPR(i,n)   for(lint i=(n)-1;i>=0;--i)
#define REPR1(i,n)  for(lint i=(n);i>0;--i)
#define REPC(i,obj) for(auto i:obj)
#define R_UP(a,b)   (((a)+(b)-1)/(b))
#define ALL(obj)    (obj).begin(),(obj).end()
#define SETP        cout << fixed << setprecision(8)
using namespace std;
using lint = long long;
template<typename T = lint>inline T in() { T x; cin >> x; return x; }

signed main() {
	int n = in(), k = in();
	bitset<28>b_bs;
	REP(i, k) {
		b_bs.set(in());
	}
	int b = b_bs.to_ulong();
	REP(i, pow(2, n)) {
		if ((i | b) == b) {
			cout << i << ':';
			int i_copy = i;
			for (int j = 0; i_copy > 0; ++j) {
				if (i_copy % 2 == 1)cout << ' ' << j;
				i_copy >>= 1;
			}
			cout << endl;
		}
	}
}