#!/usr/bin/env python
# -*- coding: utf-8 -*-

C = int(input())
N = int(input())
A = list(map(int,input().split()))

dp = [-1 for i in range(C+1)]
dp[0] = 0

for i in range(N):
    for j in range(C+1):
        if dp[j] >= 0 and j + A[i] <= C:
            if dp[j + A[i]] != -1:
                dp[j + A[i]] = min(dp[j + A[i]], dp[j] + 1)
            else:
                dp[j + A[i]] = dp[j] + 1
print(dp[C])