// Slower C++ solution:
#include <bits/stdc++.h>



const int D = 4;

const int MODN = 1e9 + 7;



struct M {

	int d[D][D];

	M() {

		memset(d, 0, sizeof d);

	}

	M operator*(const M& other) const {

		M ret;

		for (int j = 0; j < D; ++ j)

			for (int i = 0; i < D; ++ i)

				for (int k = 0; k < D; ++ k) {

					ret.d[i][k] = (1LL * d[i][j] * other.d[j][k] + ret.d[i][k]) % MODN;

				}

		return ret;

	}

};



M pw(M x, int n) {

	M ret;

	for (int i = 0; i < D; ++ i) ret.d[i][i] = 1;

	for (; n; n >>= 1, x = x * x)

		if (n & 1) ret = ret * x;

	return ret;

}



int main() {

	std::ios::sync_with_stdio(false);

	M T, cur, Tb;

	for (int i = 0; i < D; ++ i) cur.d[i][i] = 1;

	T.d[0][3] = 1;

	T.d[1][1] = T.d[1][3] = 1;

	T.d[2][1] = T.d[2][2] = T.d[2][3] = 1;

	T.d[3][1] = 1; T.d[3][2] = T.d[3][3] = 2;



	Tb.d[1][1] = 1;

	Tb.d[2][1] = Tb.d[2][2] = 1;

	Tb.d[3][1] = 1; Tb.d[3][2] = 2; Tb.d[3][3] = 1;



	int n, m; std::cin >> n >> m;

	int last = 0;

	for (int i = 0; i < m; ++ i) {

		int x; std::cin >> x;

		cur = pw(T, x - last - 1) * cur;

		cur = Tb * cur;

		last = x;

	}



	cur = pw(T, n - last) * cur;

	int ans = 0;

	for (int i = 0; i < D; ++ i)

		ans = (ans + cur.d[0][i]) % MODN;

	std::cout << ans << std::endl;

}

// Faster C++ solution for the same problem (measured speedup: 5.218191801245883x):
#include<cstdio>

#include<cstring>

#include<algorithm>

#define MAXM 100000

#define MO 1000000007

using namespace std;

struct Matrix

{

	int M[4][4];

	Matrix operator * (const Matrix &b)

	{

		Matrix ret;

		for(int i=1;i<=3;i++)

			for(int j=1;j<=3;j++)

			{

				ret.M[i][j]=0;

				for(int k=1;k<=3;k++)

					ret.M[i][j]=(1LL*ret.M[i][j]+1LL*M[i][k]*b.M[k][j]%MO)%MO;

			}

		return ret;

	}

};

int x[MAXM+5],N,M;

int finans[4],d[4];

Matrix PowMod(Matrix a,int b)

{

	Matrix ret;

	for(int i=1;i<=3;i++)

		for(int j=1;j<=3;j++)

		{

			if(i==j)

				ret.M[i][j]=1;

			else

				ret.M[i][j]=0;

		}

	while(b)

	{

		if(b&1)

			ret=ret*a;

		a=a*a;

		b>>=1;

	}

	return ret;

}

int main()

{

	scanf("%d %d",&N,&M);

	for(int i=1;i<=M;i++)

		scanf("%d",&x[i]),x[i]++;

	sort(x+1,x+1+M);

	Matrix ans,usu,ususpe;

	//===========================================

	usu.M[1][1]=1,usu.M[1][2]=0,usu.M[1][3]=0;

	usu.M[2][1]=1,usu.M[2][2]=1,usu.M[2][3]=0;

	usu.M[3][1]=1,usu.M[3][2]=2,usu.M[3][3]=1;

	//===========================================

	ususpe.M[1][1]=1,ususpe.M[1][2]=0,ususpe.M[1][3]=1;

	ususpe.M[2][1]=1,ususpe.M[2][2]=1,ususpe.M[2][3]=1;

	ususpe.M[3][1]=1,ususpe.M[3][2]=2,ususpe.M[3][3]=2;

	//===========================================

	d[1]=d[2]=d[3]=1;

	int pre=1;

	for(int i=1;i<=M;i++)

	{

		ans=PowMod(ususpe,x[i]-pre-1);

		memset(finans,0,sizeof(finans));

		for(int j=1;j<=3;j++)

			for(int k=1;k<=3;k++)

				finans[j]=(1LL*finans[j]+1LL*ans.M[j][k]*d[k]%MO)%MO;

		d[1]=finans[1],d[2]=finans[2],d[3]=finans[3];

		ans=usu;

		memset(finans,0,sizeof(finans));

		for(int j=1;j<=3;j++)

			for(int k=1;k<=3;k++)

				finans[j]=(1LL*finans[j]+1LL*ans.M[j][k]*d[k]%MO)%MO;

		d[1]=finans[1],d[2]=finans[2],d[3]=finans[3];

		pre=x[i];

	}

	ans=PowMod(ususpe,N-pre);

	memset(finans,0,sizeof(finans));

	for(int i=1;i<=3;i++)

		for(int j=1;j<=3;j++)

			finans[i]=(1LL*finans[i]+1LL*ans.M[i][j]*d[j]%MO)%MO;

	printf("%d\n",finans[3]);

	return 0;

}