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;
using ll = long long;
using ull = unsigned long long;
using vecll = vector<long long>;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define all(n) (n).begin(), (n).end()

int main()
{
    ll n, k, mask=0, b;
    cin >> n >> k;
    rep(i, k)
    {
        cin >> b;
        mask |= (1LL << b);
    }

    for (ll bit=0; bit < (1LL<<n); bit++)
    {
        vector<ll> S;
        if ((bit&mask)==bit)
        {
            for (ll i=0; i < n; i++)
            {
                if (bit & (1LL << i))
                {
                    S.push_back(i);
                }
            }

            cout << bit << ":";
            for (ll i=0;i<(ll)(S.size());i++)
            {
                cout << " " << S[i];
            }
            cout << endl;
        }
    }

}