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 <algorithm>
#include<iostream>
#include<vector>
#include<deque>
#include<queue>
#include<list>
#include<stack>
#include<map>
#include<set>
#include<string>
#include <sstream>
#include<bitset>

#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<limits.h>

using namespace std;


int main(){
  long ii,jj,kk,n,k,e;
  vector<int> a;
  bitset<32> m;
  bitset<32> t;
  bitset<32> tmp;
  int b[32];
  cin >> n;

  cin >> k;

  memset(b,0,sizeof(b));

  for(ii=0;ii<k;ii++){
    cin >> e;
    t.set(e);
    b[ii] = e;
  }
  
  int cnt;
  for(ii=0;ii<pow(2,k);ii++){
    cnt = 0;
    tmp = ii;

    for(jj=0;jj<k;jj++){
      if(tmp.test(jj)){
        //cout << "b[]" << jj << endl;
        cnt += pow(2,b[jj]);
      }
    }
    cout << cnt << ":" ;

    for(jj=0;jj<k;jj++){
      if(tmp.test(jj)){
        cout << " " << b[jj] ;
      }
    }

    cout << endl;
  }
  //for(ii=0;ii<pow(2,n);ii++){
  //  m = ii;
  //
  //  tmp = ~m  | t;
  //
  //  //cout << tmp << endl;
  //                        
  //  //cout << "ii:" << ii << endl;
  //  //cout << m << endl;
  //  //cout << t << endl;
  //  if(tmp.all()){
  //    cout << ii << ":";
  //
  //    for(jj=0;jj<n;jj++){
  //      if(m.test(jj)){
  //        cout << " " << jj;
  //      }
  //    }
  //  
  //    cout << endl;
  //  }
  //  
  //}

  
  return 0;
}