// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bit(n) (1LL<<(n))
// functions
template <typename T> void unique(T& c){c.erase(std::unique(c.begin(), c.end()), c.end());}
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

template<typename T>
T extgcd(T a, T b, T &x, T &y){ 
  T d = a;
  if(b != 0){
    d = extgcd(b, a % b, y, x);
    y -= (a / b) * x;
  }else{
    x = 1, y = 0;
  }
  return d;
}

template <typename T>
T modinv(T a, T m){
  long long x = 0, y = 0;
  extgcd<long long>(a, m, x, y);
  x %= m;
  if(x < 0)x += m;
  return x;
}


template <int MOD = int(1e9+7)>
struct LMatrix{
  vector<vector<long long>> v;
  int n, m;
  LMatrix(int n_, int m_ = -1): n(n_), m(m_){
    if(m < 0)m = n;
    v.resize(n);
    for(int i = 0; i < n; i++)v[i].resize(m);
  }
  void identity(){
    assert(n == m);
    for(int i = 0; i < n; i++){
      for(int j = 0; j < n; j++){
        v[i][j] = (i == j ? 1: 0);
      }
    }
  }
  vector<long long> &operator[](size_t i){
    return v[i];
  }
  const vector<long long> &operator[](size_t i) const{
    return v[i];
  }
  LMatrix operator*(const LMatrix &r) const{
    assert(m == r.n);
    int l = r.m;
    LMatrix res(n, l);
    for(int i = 0; i < n; i++){
      for(int j = 0; j < l; j++){
        res.v[i][j] = 0;
        for(int k = 0; k < m; k++){
          res.v[i][j] = (res.v[i][j] + v[i][k] * r.v[k][j] % MOD) % MOD;
        }
      }
    }
    return res;
  }
  LMatrix operator+(const LMatrix &r) const{
    assert(n == r.n);
    assert(m == r.m);
    LMatrix res(n, m);
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){
        res[i][j] = (v[i][j] + r[i][j]) % MOD;
      }
    }
    return res;
  }
  LMatrix operator-(const LMatrix &r) const{
    assert(n == r.n);
    assert(m == r.m);
    LMatrix res(n, m);
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){
        res[i][j] = (v[i][j] - r[i][j]) % MOD;
        if(res[i][j] < 0)res[i][j] += MOD;
      }
    }
    return res;
  }
  template <typename T>
  LMatrix operator*(T a) const{
    LMatrix res = *this;
    for(int i = 0; i < n; i++){
      for(int j = 0; j < n; j++){
        res[i][j] = a * res[i][j] % MOD;
      }
    }
    return res;
  }
  LMatrix inv2() const{
    assert(n == 2 && m == 2);
    long long det = v[0][0] * v[1][1] % MOD - v[0][1] * v[1][0] % MOD;
    if(det < 0)det += MOD;
    assert(det != 0);
    LMatrix res(2, 2);
    long long inv = modinv(det, (long long)MOD);
    res[0][0] = v[1][1];
    res[1][1] = v[0][0];
    res[1][0] = - v[1][0];
    res[0][1] = - v[0][1];
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){
        res[i][j] %= MOD;
        res[i][j] = res[i][j] * inv % MOD;
        if(res[i][j] < 0)res[i][j] += MOD;
      }
    }
    return res;
  }
};

template <typename T, int MOD = int(1e9+7)>
LMatrix<MOD> operator*(T a, const LMatrix<MOD> b){
  return b * a;
}

template <int MOD = int(1e9+7)>
LMatrix<MOD> powerm(LMatrix<MOD> &a, long long n){
  long long tmp = n;
  LMatrix<MOD> curr = a;
  LMatrix<MOD> res(a.n);
  res.identity();
  while(tmp){
    if(tmp % 2 == 1){
      res = res * curr;
    }
    curr = curr * curr;
    tmp /= 2;
  }
  return res;
}

vector<ll> mul(LMatrix<> &lm, vector<ll> &v){
  int n = sz(v);
  vector<ll> res(n, 0);
  for(int i = 0; i < n; i++){
    for(int j = 0; j < n; j++){
      (res[i] += lm[i][j] * v[j] % mod) %= mod;
    }
  }
  return res;
}

int main(){
  ll n; cin >> n;
  int m; cin >> m;
  //if(n > 1010)return 0;
  vector<ll> x(m); cin >> x;
  LMatrix<> lm(3);
  lm[0][0] = 2; lm[0][1] = 1; lm[0][2] = 1;
  lm[1][0] = 2; lm[1][1] = 1; lm[1][2] = 0;
  lm[2][0] = 1; lm[2][1] = 1; lm[2][2] = 1;
  LMatrix<> lx(3);
  lx[0][0] = 1; lx[0][1] = 0; lx[0][2] = 0;
  lx[1][0] = 2; lx[1][1] = 1; lx[1][2] = 0;
  lx[2][0] = 1; lx[2][1] = 1; lx[2][2] = 1;
  vector<ll> v = {1, 0, 0};
  /*
  int nex = 0;
  FOR(i, 1, n + 1){
    if(nex < m && x[nex] == i)v = mul(lx, v), nex++;
    else v = mul(lm, v);
    cerr << i << ": " << v << endl;
  }
  cout << v[0] << endl;
  return 0;
  //*/
  for(int i = 0; i < m; i++){
    auto pm = powerm(lm, x[i] - (i > 0 ? x[i-1]: 0) - 1);
    v = mul(pm, v);
    v = mul(lx, v);
  }
  auto pm = powerm(lm, n - (m > 0 ? x[m-1]: 0));
  v = mul(pm, v);
  cout << v[2] << endl;
  return 0;
}
  


Measured memory_bytes: 1024