#include <bits/stdc++.h>

using namespace std;

typedef long long int	ll;
typedef pair<int, int>	pii;
typedef pair<ll, ll>	pll;


#define F		        first
#define S		        second
#define pb		        push_back
#define endl            '\n'
#define Mp              make_pair
#define all(x)          x.begin(), x.end()
#define debug(x)        cerr << #x << " = " << x << endl;
#define fast_io         ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io         freopen("tests.in" , "r" , stdin) ;

ll mod = 1e9+7;

map<ll, int> mp;
ll n, m, ans;

int main()
{
    fast_io
    cin>>n>>m;
    for (int i=0; i<m; i++){
        ll x; cin>>x;
        mp[x]=1;
    }
    while(n!=1){
        for (auto &pp: mp){
            if(pp.F<=n/2){
                if(mp[n-pp.F+1]!=pp.S && (pp.S==2 || mp[n-pp.F+1]==2)) pp.S=min(pp.S, mp[n-pp.F+1]);
                if(mp[n-pp.F+1]!=pp.S && !(pp.S==2 || mp[n-pp.F+1]==2)){pp.S=2; ans++;}
            }
            else{
                if(mp.count(n-pp.F+1))continue;
                if(pp.S!=2){
                    mp[n-pp.F+1]=2;
                    ans++;
                }
            }

        }
        while(1){
            if(mp.empty()) break;
            auto x=mp.end(); x--;
            if((x->F)>n/2) mp.erase(x);
            else break;
        }
        n>>=1;
    }
    cout<<ans<<endl;
}