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 int long long
#define resz(v, ...) (v).clear(), (v).resize(__VA_ARGS__)
#define reps(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
#define rep(i, n) reps(i, 0, n)


using Pi = pair<int, int>;
using Tapris = tuple<int, int, int>;
using vint = vector<int>;

signed main() {
    int n, m, c = 0;
    cin >> n >> m;
    rep(i, m) {
        int x;
        cin >> x;
        c |= 1 << x;
    }
    rep(b, (1 << n)) {
        if ((b | c) != c) continue;
        cout << b << ":";
        rep(i, n) {
            if (b & (1 << i)) {
                cout << " " << i;
            }
        }
        cout << endl;
    }
    cout << flush;
    return 0;
}