#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3dSgv16 ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
// e
signed main(){
_3dSgv16;
int n,k;
cin>>n>>k;
assert(n<=5e6);
vi usd(n+1,0);
rep(i,k){
int v;
cin>>v;
for(int j=v;j<=n;j+=v){
usd[j]=1;
}
}
usd[n]=1;
usd[0]=1;
int ans=0;
rng(i,1,n+1){
if(usd[i] and usd[i-1]){
ans+=1;
}
}
print(ans);
}
