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 <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <map>
#include <numeric>
#include <string>
#include <cmath>
#include <iomanip>
#include <queue>
#include <list>
#include <set>
#include <stack>
#include <cctype>
#include <cmath>
#include <bitset>

using namespace std;

/* typedef */
typedef long long ll;

/* constant */
const int INF = 1 << 30;
const int NIL = -1;
const int MAX = 10000;
const int mod = 1000000007;
const double pi = 3.141592653589;

/* global variables */

/* function */

/* main */
int main(){

    int n, m, x;
    cin >> n >> m;
    bitset<28> mask(0);
    for (int i = 0; i < m; i++) {
        cin >> x;
        mask.set(x);
    }
    // Print bit if binary(i) includes only mask bits

    /*
    // 1 ============================
    for (int i = 0; i < (1 << n); i++) {
        bitset<28> bs(i);
        if ((bs | mask) == mask) {
            printf("%d:", i);
            for (int j = 0; j < n; j++) {
                if ((bs >> j)[0]) printf(" %d", j);
            } 
            printf("\n");
        }
    }
    */

    // 2 ===========================
    int mask_int = mask.to_ulong();
    for (int b = 0; b < (1 << n); b++) {
        if ((b | mask_int) == mask_int) {
            printf("%d:", b);
            for (int i = 0; i < n;i++)
                if( (b >> i) & 1)
                    printf(" %d", i);
            printf("\n");
        }
    }

}