Problem:
Score : 400 points

Problem Statement

Find the largest integer that can be formed with exactly N matchsticks, under the following conditions:

Every digit in the integer must be one of the digits A_1, A_2, ..., A_M (1 \leq A_i \leq 9).

The number of matchsticks used to form digits 1, 2, 3, 4, 5, 6, 7, 8, 9 should be 2, 5, 5, 4, 5, 6, 3, 7, 6, respectively.

Constraints

All values in input are integers.

2 \leq N \leq 10^4

1 \leq M \leq 9

1 \leq A_i \leq 9

A_i are all different.

There exists an integer that can be formed by exactly N matchsticks under the conditions.

Input

Input is given from Standard Input in the following format:

N M
A_1 A_2 ... A_M

Output

Print the largest integer that can be formed with exactly N matchsticks under the conditions in the problem statement.

Sample Input 1

20 4
3 7 8 4

Sample Output 1

777773

The integer 777773 can be formed with 3 + 3 + 3 + 3 + 3 + 5 = 20 matchsticks, and this is the largest integer that can be formed by 20 matchsticks under the conditions.

Sample Input 2

101 9
9 8 7 6 5 4 3 2 1

Sample Output 2

71111111111111111111111111111111111111111111111111

The output may not fit into a 64-bit integer type.

Sample Input 3

15 3
5 4 6

Sample Output 3

654

Solution in Rust (1.42.0) (judge verdict: Accepted)

use std::cmp::*;
use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let m: usize = itr.next().unwrap().parse().unwrap();
    let mut a: Vec<usize> = (0..m)
        .map(|_| itr.next().unwrap().parse::<usize>().unwrap() - 1)
        .collect();
    a.sort_by(|a, b| b.cmp(a));
    let b = [2, 5, 5, 4, 5, 6, 3, 7, 6].to_vec();
    let mut dp = vec![-1; n + 1];
    let mut prv = vec![0; n + 1];

    dp[0] = 0;
    for i in 1..=n {
        for j in 0..m {
            if i >= b[a[j]] {
                let tmp = dp[i - b[a[j]]] + 1;
                if tmp > dp[i] {
                    dp[i] = tmp;
                    prv[i] = a[j];
                }
            }
        }
    }

    let mut ans = Vec::new();
    let mut i = n;
    while i > 0 {
        ans.push((49 + prv[i] as u8) as char);
        i -= b[prv[i]];
    }
    println!("{}", ans.into_iter().collect::<String>());
}