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<bits/stdc++.h>

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

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

#define MAX 100005
#define INF 1001001001

int main(int, char**)
{
  int n;
  cin >> n;
  int k;
  cin >> k;
  bitset<28> mask(0);
  rep(i,k) {
    int b; cin >> b;
    mask.set(b);
  }

  rep(i,1<<n) {
    bitset<28> b(i);
    if ((b&~mask).any()) continue;
    cout << i << ":";
    rep(j,n) if (b[j]) cout << " " << j;
    cout << endl;
  }

  return 0;
}