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;


int main(){
    int n,k;
    int temp;
    int mask = 0;
    scanf("%d",&n);
    scanf("%d",&k);

    for(int i = 0;i < k;i++){
        scanf("%d",&temp);
        mask |= (1 << temp);
    }

    for(int i = 0; i < (1 << n);i++){
        if((i | mask)  == mask){
            printf("%d:",i);
            for(int j = 0;j < n;j++){
                if( i&(1<<j) ) printf(" %d",j);
            }
            printf("\n");
        } 
    }
    
    return 0;   
}