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;
using UL = unsigned int;
using ULL = unsigned long long;
using LL = long long;
#define rep(i, n) for(UL i = 0; i < (n); i++)

struct Problem {
public:

	void Solve() {
		UL N; scanf("%d", &N);
		UL M = 0;
		UL K; scanf("%d", &K);
		rep(i, K) {
			UL m; scanf("%d", &m);
			M |= (1 << m);
		}
		UL p = M;
		rep(k, 1 << K) {
			printf("%d:", (M ^ p));
			rep(j, N) {
				if (((M ^ p) >> j) & 1) printf(" %d", j);
			}
			printf("\n");
			p = M & (p - 1);
		}
	}
};

int main() {
	unique_ptr<Problem> p(new Problem());
	p->Solve();
	return 0;
}