#include<bits/stdc++.h>

using namespace std;

struct INIT{
    INIT(){
	ios::sync_with_stdio(false);
	cin.tie(0);
    }
}init;
#define rep(i,n) for(auto i=(n)*0;i<n;i++)
const int INF=11*4*51*4*1919;
int main(){
    int M,N;
    cin>>M>>N;
    vector<int> dp(M+1,-INF),C(N);
    dp[M]=0;
    rep(i,N)cin>>C[i];
    rep(i,M){
	rep(j,N){
	    int from=M-i;
	    int to=from-C[j];
	    if(to>=0)dp[to]=max(dp[to],dp[from]+1);
	}
    }
    vector<bool> isprime(M+1,true);
    isprime[0]=isprime[1]=false;
    int sum=0;
    for(int i=2;i*i<=M;i++)
	if(isprime[i]){
	    for(int j=i+i;j<=M;j+=i)
		isprime[j]=false;
	}
    rep(i,M+1)if(isprime[i]&&dp[i]>=0)sum+=dp[i];
    int res=0;
    rep(i,M+1)res=max(res,sum+dp[i]);
    cout<<res<<endl;
    return 0;
}