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;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define repc(i, b, e) for(auto i = (b); i != (e); i++)

int main(){
    int n, k, t;
    cin >> n;
    ll x = 0, e = pow(2, n);
    cin >> k;
    rep(i, k){
        cin >> t;
        x += (1<<t);
    }
    repc(i, 0LL, e){
        if((i & x) == i){
            bitset<30> xx(i);
            cout << i << ":";
            rep(j, n){
                if (xx.test(j)){
                    cout << " " << j;
                }
            }
        cout << endl;
        }
    }
    return 0;
}