/*
    IN THE NAME OF GOD
*/
#include <bits/stdc++.h>

// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

using namespace std;

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

#define F                                      first
#define S                                      second
#define Mp                                     make_pair
#define pb                                     push_back
#define pf                                     push_front
#define size(x)                                ((ll)x.size())
#define all(x)                                 (x).begin(),(x).end()
#define kill(x)		                           cout << x << '\n', exit(0);
#define fuck(x)                                cout << "(" << #x << " , " << x << ")" << endl
#define endl                                   '\n'

const int N = 3e5+23, lg = 18;
ll Mod = 1e9+7; //998244353;

inline ll MOD(ll a, ll mod=Mod) {a%=mod; (a<0)&&(a+=mod); return a;}
inline ll poww(ll a, ll b, ll mod=Mod) {
    ll ans = 1;
    a=MOD(a, mod);
    while (b) {
        if (b & 1) ans = MOD(ans*a, mod);
        b >>= 1;
        a = MOD(a*a, mod);
    }
    return ans;
}

ll t, n, m, a[N], dp[2][20*N], cnt;
set<ll> st;
map<ll, bool> mp;

void divide(int id, ll v, ll h) {
    if(mp[v] == 0) {
        dp[0][id] = 0, dp[1][id] = n/(1ll<<h);
        return;
    }
    if((1ll<<h) == n) {
        if(st.find(v)!=st.end()) {
            dp[0][id] = 1, dp[1][id] = 0;
        } else {
            dp[1][id] = 1, dp[0][id] = 0;
        }
        return;
    }

    ll lft=++cnt, rgt=++cnt;
    divide(lft, v, h+1); divide(rgt, (1ll<<(h+1))-v+1, h+1);

    dp[0][id] = min({
        dp[0][lft]+dp[0][rgt],
        dp[0][lft]+dp[1][rgt]+1,
        dp[1][lft]+dp[0][rgt]+1,
        dp[1][lft]+dp[1][rgt]+2
    });
    dp[1][id] = min({
        dp[0][lft]+dp[0][rgt]+2,
        dp[0][lft]+dp[1][rgt]+1,
        dp[1][lft]+dp[0][rgt]+1,
        dp[1][lft]+dp[1][rgt]
    });
}

int main () {
	ios_base::sync_with_stdio(false), cin.tie(0);

	cin>>n>>m; 
    ll num = 0;
    while((1ll<<num) < n) num++;
    
    // fuck(num);
    for(int i=1; i<=m; i++) {
        ll x; cin>>x;
        st.insert(x);
        
        mp[x] = 1;
        for(ll h=num; h>0; h--) {
            x = (1ll<<h) - x + 1;
            mp[x] = 1;
        }
    }
    mp[1] = 1;

    divide(++cnt, 1, 0);
    cout<<min(dp[0][1], dp[1][1]);

	return 0;
}