#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const ld EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

template<ll mod>
struct Mod_Int{
    ll x;
    Mod_Int() {}
    Mod_Int(ll y) : x (y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    Mod_Int &operator += (const Mod_Int &p){
        x = (x + p.x) % mod;
        return *this;
    }

    Mod_Int &operator -= (const Mod_Int &p){
        x = (x + mod - p.x) % mod;
        return *this;
    }

    Mod_Int &operator *= (const Mod_Int &p){
        x = (x * p.x) % mod;
        return *this;
    }

    Mod_Int &operator /= (const Mod_Int &p){
        *this *= p.inverse();
        return *this;
    }

    Mod_Int &operator ^= (ll k){
        Mod_Int ret = 1;
        while(k){
            if(k&1) ret *= *this;
            *this *= *this, k >>= 1;
        }
        swap(x, ret.x);
        return *this;
    }

    Mod_Int &operator ++ () {return *this += Mod_Int(1);}

    Mod_Int operator ++ (int){
        Mod_Int tmp = *this;
        ++*this;
        return tmp;
    }

    Mod_Int &operator -- () {return *this -= Mod_Int(1);}

    Mod_Int operator -- (int){
        Mod_Int tmp = *this;
        --*this;
        return tmp;
    }

    Mod_Int operator - () const {return Mod_Int(-x);}

    Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}

    Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}

    Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}

    Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}

    Mod_Int operator ^ (ll k) const {return Mod_Int(*this) ^= k;}

    bool operator == (const Mod_Int &p) const {return x == p.x;}

    bool operator != (const Mod_Int &p) const {return x != p.x;}

    Mod_Int inverse() const {return *this ^ (mod-2);}

    friend ostream &operator << (ostream &os, const Mod_Int &p){
        return os << p.x;
    }

    friend istream &operator >> (istream &is, Mod_Int &p){
        ll a;
        is >> a;
        p = Mod_Int<mod>(a);
        return is;
    }
};

using mint = Mod_Int<MOD>;
const int MAX_N = 1000000;
mint fac[MAX_N+1], ifac[MAX_N+1];

void init(){
    fac[0] = 1;
    rep2(i, 1, MAX_N){
        fac[i] = fac[i-1]*i;
    }
    ifac[MAX_N] = fac[MAX_N].inverse();
    rep3(i, MAX_N, 1){
        ifac[i-1] = ifac[i]*i;
    }
}

mint comb(int n, int k){
    return fac[n]*ifac[n-k]*ifac[k];
}

mint perm(int n, int k){
    return fac[n]*ifac[n-k];
}

template<class T>
struct Matrix{
    vector<vector<T>> A;
    const int n, m;
    Matrix() {}
    Matrix(int n, int m) : A(n, vector<T>(m, 0)), n(n), m(m) {} //+の単位元

    inline const vector<T> &operator [] (int k) const{
        return A[k];
    }

    inline vector<T> &operator [] (int k){
        return A[k];
    }

    static Matrix I(int l){
        Matrix ret(l, l);
        rep(i, l) ret[i][i] = 1; //*の単位元
        return ret;
    }

    Matrix &operator *= (const Matrix &B){
        int p = B.m;
        assert(m == B.n);
        Matrix tmp(n, p);
        rep(i, n){
            rep(k, m){
                rep(j, p) tmp.A[i][j] += A[i][k]*B[k][j];
            }
        }
        swap(A, tmp.A);
        return *this;
    }

    Matrix &operator ^= (ll k){
        assert(n == m);
        Matrix ret = I(n);
        while(k > 0){
            if(k&1) ret *= *this;
            *this *= *this, k >>= 1;
        }
        swap(A, ret.A);
        return *this;
    }

    Matrix operator * (const Matrix &B) const {return Matrix(*this) *= B;}

    Matrix operator ^ (ll k) const {return Matrix(*this) ^= k;}
};

int main(){
    int N, M;
    cin >> N >> M;
    int d[M+2];
    d[0] = 0, d[M+1] = N;
    rep2(i, 1, M) cin >> d[i];
    Matrix<mint> A(4, 4), B(4, 4), x(4, 1), ret(4, 4);
    rep(i, 4){
        rep(j, 4){
            if((i|j) == i) A[i][j] = 1;
        }
    }
    rep(i, 4) B[i][i] = 1, ret[i][i] = 1;
    B[0][3] = 1, x[0][0] = 1;
    rep(i, M+1){
        ret *= (A*B)^(d[i+1]-d[i]-1);
        ret *= A;
    }
    ret *= x;
    cout << ret[3][0] << endl;
}

Measured memory_bytes: 3876