#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


template<typename K>
struct Matrix{
  typedef vector<K> arr;
  typedef vector<arr> mat;
  mat dat;

  Matrix(size_t r,size_t c):dat(r,arr(c,K())){}
  Matrix(mat dat):dat(dat){}

  size_t size() const{return dat.size();};
  bool empty() const{return size()==0;};
  arr& operator[](size_t k){return dat[k];};
  const arr& operator[](size_t k) const {return dat[k];};
  
  static Matrix cross(const Matrix &A,const Matrix &B){
    Matrix res(A.size(),B[0].size());    
    for(int i=0;i<(int)A.size();i++)
      for(int j=0;j<(int)B[0].size();j++)
        for(int k=0;k<(int)B.size();k++)
          res[i][j]+=A[i][k]*B[k][j];
    return res;
  }

  static Matrix identity(size_t n){
    Matrix res(n,n);
    for(int i=0;i<(int)n;i++) res[i][i]=K(1);
    return res;
  }
  
  Matrix pow(long long n) const{
    Matrix a(dat),res=identity(size());
    while(n){
      if(n&1) res=cross(res,a);
      a=cross(a,a);      
      n>>=1;
    }
    return res;
  }

  template<typename T> using ET = enable_if<is_floating_point<T>::value>;
  template<typename T> using EF = enable_if<!is_floating_point<T>::value>;
  
  template<typename T, typename ET<T>::type* = nullptr>
  static bool is_zero(T x){return abs(x)<1e-8;}
  template<typename T, typename EF<T>::type* = nullptr>
  static bool is_zero(T x){return x==T(0);}

  static Matrix gauss_jordan(const Matrix &A,const Matrix &B){
    int n=A.size(),l=B[0].size();
    Matrix C(n,n+l);
    for(int i=0;i<n;i++){
      for(int j=0;j<n;j++)
        C[i][j]=A[i][j];      
      for(int j=0;j<l;j++)
        C[i][n+j]=B[i][j];
    }
    for(int i=0;i<n;i++){
      int p=i;
      for(int j=i;j<n;j++)
        if(abs(C[p][i])<abs(C[j][i])) p=j;
      swap(C[i],C[p]);
      if(is_zero(C[i][i])) return Matrix(0,0);
      for(int j=i+1;j<n+l;j++) C[i][j]/=C[i][i];
      for(int j=0;j<n;j++){
        if(i==j) continue;
        for(int k=i+1;k<n+l;k++)
          C[j][k]-=C[j][i]*C[i][k];
      }
    }
    Matrix res(n,l);
    for(int i=0;i<n;i++)
      for(int j=0;j<l;j++)
        res[i][j]=C[i][n+j];
    return res;
  }
  
  Matrix inv() const{
    Matrix B=identity(size());
    return gauss_jordan(*this,B);
  }
  
  K determinant() const{
    Matrix A(dat);
    K res(1);
    int n=size();
    for(int i=0;i<n;i++){
      int p=i;
      for(int j=i;j<n;j++)
        if(abs(A[p][i])<abs(A[j][i])) p=j;      
      if(i!=p) swap(A[i],A[p]),res=-res;      
      if(is_zero(A[i][i])) return K(0);      
      res*=A[i][i];
      for(int j=i+1;j<n;j++) A[i][j]/=A[i][i];
      for(int j=i+1;j<n;j++)
        for(int k=i+1;k<n;k++)
          A[j][k]-=A[j][i]*A[i][k];
    }
    return res;
  }

  static arr linear_equations(const Matrix &A,const arr &b){
    Matrix B(b.size(),1);
    for(int i=0;i<(int)b.size();i++) B[i][0]=b[i];
    Matrix tmp=gauss_jordan(A,B);
    arr res(tmp.size());
    for(int i=0;i<(int)tmp.size();i++) res[i]=tmp[i][0];
    return res;
  }
  
  static K sigma(K x,long long n){
    Matrix A(2,2);
    A[0][0]=x;A[0][1]=0;
    A[1][0]=1;A[1][1]=1;
    return A.pow(n)[1][0];
  }
};


template<typename T,T MOD = 1000000007>
struct Mint{
  T v;
  Mint():v(0){}
  Mint(signed v):v(v){}
  Mint(long long t){v=t%MOD;if(v<0) v+=MOD;}

  Mint pow(int k){
    Mint res(1),tmp(v);
    while(k){
      if(k&1) res*=tmp;
      tmp*=tmp;
      k>>=1;
    }
    return res;
  }
  
  Mint inv(){return pow(MOD-2);}
  
  Mint& operator+=(Mint a){v+=a.v;if(v>=MOD)v-=MOD;return *this;}
  Mint& operator-=(Mint a){v+=MOD-a.v;if(v>=MOD)v-=MOD;return *this;}
  Mint& operator*=(Mint a){v=1LL*v*a.v%MOD;return *this;}
  Mint& operator/=(Mint a){return (*this)*=a.inv();}
  
  Mint operator+(Mint a) const{return Mint(v)+=a;};
  Mint operator-(Mint a) const{return Mint(v)-=a;};
  Mint operator*(Mint a) const{return Mint(v)*=a;};
  Mint operator/(Mint a) const{return Mint(v)/=a;};

  Mint operator-(){return v?MOD-v:v;}

  bool operator==(const Mint a)const{return v==a.v;}
  bool operator!=(const Mint a)const{return v!=a.v;}

};

//INSERT ABOVE HERE
signed main(){
  int n,m;
  cin>>n>>m;
  vector<int> x(m);
  for(int i=0;i<m;i++) cin>>x[i];
  x.emplace(x.begin(),0);
  x.emplace_back(n);

  using M = Mint<int>;
  using MM = Matrix<M>;

  MM A(3,3);
  A[0][0]=2;A[0][1]=1;A[0][2]=1;
  A[1][0]=2;A[1][1]=1;A[1][2]=0;
  A[2][0]=1;A[2][1]=1;A[2][2]=1;
  
  MM B(3,3);
  B[0][0]=1;B[0][1]=0;B[0][2]=0;
  B[1][0]=2;B[1][1]=1;B[1][2]=0;
  B[2][0]=1;B[2][1]=1;B[2][2]=1;

  MM C(3,1);
  C[0][0]=1;
  C[1][0]=0;
  C[2][0]=0;
  
  for(int i=0;i<=m;i++){
    int l=(x[i+1]-x[i])-1;
    C=MM::cross(A.pow(l),C);
    if(i!=m) C=MM::cross(B,C);
  }

  M ans(0);
  ans+=C[0][0];
  ans+=C[1][0];
  ans+=C[2][0];

  cout<<ans.v<<endl;
  return 0;
}


Measured memory_bytes: 1024