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 Go (1.6) (judge verdict: Accepted)

package main
 
import (
  "fmt"
  "strconv"
)

func max(A string, B string) string {
  if len(A) > len(B) || (len(A) == len(B) && A > B){
    return A
  }
  return B
}

func main() {
  var N, M int
  fmt.Scan(&N, &M)
  A := make([][]int, M)
  B := []int{0, 2, 5, 5, 4, 5, 6, 3, 7, 6}
  DP := make([]string, N + 1)
  var x int
  for i, _ := range A {
    fmt.Scan(&x)
    A[i] = []int{B[x], x}
    if B[x] <= N {
      DP[B[x]] = max(DP[B[x]], strconv.Itoa(x))
    }
  }
  for i, _ := range DP {
    for _, a := range A {
      if i > a[0] && len(DP[i - a[0]]) >= 1 {
        b := DP[i - a[0]] + strconv.Itoa(a[1])
        DP[i] = max(DP[i], b)
      }
    }
  }
  fmt.Println(DP[N])
}