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 JAVA):

Solution:
import java.util.Scanner;
class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int k = sc.nextInt();
			int tBit = 0;
			for(int i = 0; i < k; i++) {
				int j = sc.nextInt();
				if((tBit>>j&1)==0)
					tBit += 1<<j;
			}
			System.out.println("0:");
			for (int bit = 1; bit < (1<<n); bit++) {
				if((bit&~tBit) == 0 && (bit&tBit) != 0) {
					System.out.print(bit + ":");
					for (int j = 0; j < n; j++) {
						if (((bit>>j) & 1) == 1) {
							System.out.print(" " + j);
						}
					}
					System.out.println();
				}
			}
		}
	}
}