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::vec::Vec;
use std::cmp;
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn main() {
    let (n, m) = {
      let v: Vec<usize> = read_vec();
      (v[0], v[1])
    };

    let mut a: Vec<u64> = read_vec();
    a.sort_by(|a, b| b.cmp(&a));
    let mut dp: Vec<MatchNumber> = vec![MatchNumber {length: 0, number: Vec::new()}; n+1];
    let mut mtchs = vec![0; n+1];

    for i in 1..n+1 {
      for &e in &a {
        if i < f(e)  {
          continue;
        }
        else {
          if mtchs[i - f(e)] + f(e) != i {
            continue;
          }
          else {
            mtchs[i] = i;
            let mut m = dp[i - f(e)].clone();
            m.push(e);
            dp[i] = cmp::max(dp[i].clone(), m);
          }
        }
      }
    }


    for &e in  &dp[n].number {
      print!("{}", e);
    }
    println!("");
}

fn f(x: u64) -> usize {
  match x {
    1 => 2,
    2 => 5,
    3 => 5,
    4 => 4,
    5 => 5,
    6 => 6,
    7 => 3,
    8 => 7,
    9 => 6,
    _ => std::usize::MAX/2
  }
}




#[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Debug)]
struct MatchNumber {
  length: i64,
  number: Vec<u64>,
}

impl MatchNumber {
  pub fn new() -> MatchNumber {
    MatchNumber {length: 0, number: Vec::new()}
  }

  fn push(&mut self, c: u64) {
    self.length += 1;
    self.number.push(c);
  }


}