#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
  int n,m;cin>>n>>m;
  vector<int> A(m);
  for(int i = 0; m > i; i++){
    cin>>A[m-i-1];
  }
  vector<int> B(n+1);
  int ans = 0;
  int nw = 0;
  for(int i = n; 0 < i; i--){
    bool odd = false;
    if(nw != m && A[nw] == i){
      odd = true;
      nw++;
    }
    if(B[i]%2 != odd){
      //used
      for(int j = 1; i >= j*j; j++){
        if(i%j == 0){
          B[j]++;
          if(j*j!=i)B[i/j]++;
        }
      }

    }else{
      ans++;
    }
  }
  cout << ans << endl;
}