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)


const num_chars: [char; 9] = ['1', '2', '3', '4', '5', '6', '7', '8', '9'];
const num_stick: [usize; 9] = [2, 5, 5, 4, 5, 6, 3, 7, 6];

fn func(input_str: &str) -> String {
    let mut iter = input_str.split_whitespace();
    let n: usize = iter.next().unwrap().parse().unwrap();
    let m: usize = iter.next().unwrap().parse().unwrap();
    let mut a_s: Vec<usize> = iter.take(m).map(|x| x.parse().unwrap()).collect();
    a_s.sort();
    a_s.reverse();
    let a_s = a_s;

    let mut dp = vec![std::isize::MIN; n + 1];
    dp[0] = 0;
    for i in 1..(n + 1) {
        for &a in &a_s[..] {
            let ns = num_stick[a - 1];
            if i >= ns {
                dp[i] = std::cmp::max(dp[i], dp[i - ns] + 1);
            }
        }
    }

    let mut ans = Vec::new();
    let mut r_stick = n;
    while r_stick > 0 {
        for &a in &a_s[..] {
            if r_stick >= num_stick[a - 1] && dp[r_stick] - 1 == dp[r_stick - num_stick[a - 1]] {
                ans.push(num_chars[a - 1]);
                r_stick -= num_stick[a - 1];
                break;
            }
        }
    }
    ans.into_iter().collect()
}

use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    println!("{}", func(&buf[..]));
}