#include<bits/stdc++.h>
 
#define HEAP priority_queue
#define rep(i, n) for(int i = 0, _end_ = (n); i < _end_; ++i)
#define per(i, n) for(int i = (n) - 1; i >= 0 ; --i)
#define forn(i, l, r) for(int i = (l), _end_ = (r); i <= _end_; ++i)
#define nrof(i, r, l) for(int i = (r), _end_ = (l); i >= _end_; --i)
#define FOR(a, b) for(auto (a): (b))
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define X first
#define Y second
#define eps 1e-6
#define pi 3.1415926535897932384626433832795
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(), x.end()
#define FILL(a, b) memset((a), (b), sizeof((a)))
#define MCPY(a, b) memcpy((a), (b), sizeof((b)))
 
using namespace std;
 
typedef long long LL;
typedef double flt;
typedef vector<int> vi;
typedef vector<LL> vl;
typedef pair<int,int> pii;
typedef pair<int,LL> pil;
typedef pair<LL,int> pli;
typedef pair<LL,LL> pll;
typedef vector<pil> vil;
typedef vector<pii> vii;
typedef vector<pli> vli;
typedef vector<pll> vll;
 
const int iinf = 1e9 + 7;
const int oo = 0x3f3f3f3f;
const LL linf = 1ll << 60;
const flt dinf = 1e60;
 
template <typename T>
inline void scf(T &x)
{
	bool f = 0; x = 0; char c = getchar();
	while((c < '0' || c > '9') && c != '-') c = getchar();
	if(c == '-') { f = 1; c = getchar(); }
	while(c >= '0' && c <= '9') { x = x * 10 + c - '0'; c = getchar(); }
	if(f) x = -x; return;
}
template <typename T1, typename T2>
void scf(T1 &x, T2 &y) { scf(x); return scf(y); }
template <typename T1, typename T2, typename T3>
void scf(T1 &x, T2 &y, T3 &z) { scf(x); scf(y); return scf(z); }
template <typename T1, typename T2, typename T3, typename T4>
void scf(T1 &x, T2 &y, T3 &z, T4 &w) { scf(x); scf(y); scf(z); return scf(w); }
 
inline char mygetchar(){ char c = getchar(); while(c == ' ' || c == '\n') c = getchar(); return c; }
 
template <typename T> inline bool chkmax(T &x, const T &y){ return y > x ? x = y, 1 : 0; }
template <typename T> inline bool chkmin(T &x, const T &y){ return y < x ? x = y, 1 : 0; }
 
#define ONLINE_JUDGE
 
#ifdef ONLINE_JUDGE
#define debug(...) ;
#else
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define DEBUG
#endif
 
//---------------------------------------------------------head----------------------------------------------------
 
const int mat1[4][4] = {{1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}};
const int mat2[4][4] = {{1, 0, 0, 1}, {1, 1, 0, 1}, {1, 0, 1, 1}, {1, 1, 1, 2}};
 
struct MATH
{
	static const int mod = 1e9 + 7;
 
	inline void add(int &x, const int &y){ x = (x + y < mod) ? (x + y) : (x + y - mod); }
	inline int multi(const int &x, const int &y){ return 1ll * x * y % mod; }
	inline int sum(const int &x, const int &y){ return (x + y < mod) ? (x + y) : (x + y - mod); }
}math;
 
struct mat
{
	int num[4][4];
 
	mat(){ FILL(num, 0); }
 
	mat operator *(const mat &a) const
	{
		mat ret;
		rep(i, 4) rep(j, 4) rep(k, 4) math.add(ret.num[i][j], math.multi(num[i][k], a.num[k][j]));
		return ret;
	}
 
	void B()
	{
		memcpy(num, mat2, sizeof(mat2));
		return;
	}
 
	void I()
	{
		memcpy(num, mat1, sizeof(mat1));
		return;
	}
 
	void C(const mat &a)
	{
		memcpy(num, a.num, sizeof num);
		return;
	}
}A, B, C;
 
int n, m;
int dp[4] = {1, 1, 1, 1}, pd[4];
 
mat mat_pow(int n)
{
	B.I(); C.C(A);
	while(n)
	{
		if(n & 1) B = B * C;
		C = C * C;
		n >>= 1;
	}
	return B;
}
 
int main()
{
	scf(n, m);
	A.B();
	int lst = 0;
	while(m--)
	{
		int x; scf(x);
		mat D = mat_pow(x - lst - 1);
		memset(pd, 0, sizeof(pd));
		rep(i, 4) rep(j, 4) math.add(pd[i], math.multi(D.num[i][j], dp[j]));
#ifdef DEBUG
		rep(i, 4) printf("%d ", pd[i]); putchar('\n');
#endif
		dp[0] = pd[0];
		dp[1] = math.sum(pd[0], pd[1]);
		dp[2] = math.sum(pd[0], pd[2]);
		dp[3] = math.sum(math.sum(pd[0], pd[1]), math.sum(pd[2], pd[3]));
#ifdef DEBUG
		rep(i, 4) printf("%d ", dp[i]); putchar('\n');
#endif
		lst = x;
	}
	mat D = mat_pow(n - lst - 1);
#ifdef DEBUG
	rep(i, 4)
	{
		rep(j, 4) printf("%d ", D.num[i][j]);
		putchar('\n');
	}
#endif
	memset(pd, 0, sizeof(pd));
	rep(i, 4) rep(j, 4) math.add(pd[i], math.multi(D.num[i][j], dp[j]));
	printf("%d\n", pd[3]);
	return 0;
}

Measured memory_bytes: 256