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::str::FromStr;
use std::fmt::Debug;
use std::cmp;
fn read_as_vec<T>() -> Vec<T>
where T: FromStr, <T as FromStr>::Err : Debug{
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().split_whitespace().map(|c| T::from_str(c).unwrap()).collect()

}

fn read_as_string() -> String{
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().to_string()
}

fn main(){
    let line: Vec<usize> = read_as_vec();
    let (n, m) = (line[0], line[1]);
    let kinds: Vec<usize> = read_as_vec();
     //                           0, 1, 2, 3, 4, 5, 6, 7, 8, 9
    let costs: Vec<usize> = vec![0, 2, 5, 5, 4, 5, 6, 3, 7, 6];
    let mut kind_cost: Vec<(usize, usize)> = Vec::new();

    for kind in &kinds{
        kind_cost.push((*kind, costs[*kind]));
    }

    
    //determine the number of digits
    let mut digits: Vec<Option<u32>> = vec![None;n+1];
    digits[0] = Some(0);

    for i in 0..n+1{
        let mut biggest = None;
        for &(_, cost) in &kind_cost{
            if i < cost{ continue;}
            if let Some(x) = digits[i-cost]{
                biggest = cmp::max(Some(x+1), biggest);
            }


        }

        digits[i] = cmp::max(biggest, digits[i]);
    }

    //println!("{:?}", digits);

    kind_cost.sort();
    kind_cost.reverse();
    //println!("{:?}", kind_cost);


    let mut num_match = n;
    for _ in 0..digits[n].unwrap(){
        for &(kind, cost) in &kind_cost{
            if num_match < cost{
                continue;
            }
            if digits[num_match-cost].is_none(){
                continue;
            }
            
            if (num_match >= cost && digits[num_match - cost].unwrap() == digits[num_match].unwrap() - 1) &&
                (digits[num_match].unwrap() - 1 != 0 || num_match == cost){
                print!("{}", kind);
                num_match -= cost;
                break;
            }

        }
    }

    println!("");
}