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 (1.15.1) (judge verdict: Accepted)

use std::io::Read;

fn check(a: String, b: String) -> String {
    if a == "unko" {
        b
    } else if a.len() > b.len() {
        a
    } else if a.len() < b.len() {
        b
    } else {
        let c: Vec<char> = a.chars().collect();
        let d: Vec<char> = b.chars().collect();
        for i in 0..a.len() {
            if c[i] > d[i] {
                return a;
            } else if c[i] < d[i] {
                return b;
            }
        }
        b
    }
}

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 a: Vec<usize> = (0..m)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();
    let need: Vec<usize> = [0, 2, 5, 5, 4, 5, 6, 3, 7, 6].to_vec();
    let mut dp: Vec<String> = vec!["unko".to_string(); n + 9];
    dp[0] = "".to_string();
    for i in 0..n {
        for &j in a.iter() {
            if dp[i] == "unko" {
                continue;
            }
            dp[i + need[j]] = check(dp[i + need[j]].clone(), dp[i].clone() + &j.to_string());
        }
    }
    println!("{}", dp[n]);
}