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 PYTHON3):

Solution:
n=int(input())
ind='0'+str(n)+'b'

t=list(map(int,input().split()))
k=t[0]
t.pop(0)
T=t
T.reverse()
ind='0'+str(k)+'b'

for i in range(2**k):
    compare=[int(j) for j in format(i,ind)]
    disp=[T[j] for j in range(k) if compare[j]==1]
    disp.reverse()
    if len(disp)==0:
        print("0:")
    else:
        calc=[2**j for j in disp]
        print(str(sum(calc))+":",end="")
        print(" "+' '.join(map(str,disp)))