#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define llu unsigned long long
#define ld double
#define llu unsigned long long
#define rep(i,x,y)  for(int i=int(x);i<int(y);++i)
#define For(i,x,y)  for(int i=int(x);i<=int(y);++i)
#define FOr(i,x,y)  for(int i=int(x);i>=int(y);--i)
#define pi acos(-1) 
#define mk make_pair
#define pa pair<ll,ll>
#define lf else if
#define IL inline
#define max(x,y)    ((x)<(y)?(y):(x))
#define min(x,y)    ((x)<(y)?(x):(y))
#define sqr(x)      ((x)*(x))
#define Mul(x,y)    ((x)=1LL*(x)*(y)%mod)
#define Add(x,y)    ((x)=((x)+(y))%mod)
#define Max(x,y)    ((x)=((x)<(y)?(y):(x)))
#define Min(x,y)    ((x)=((x)>(y)?(y):(x)))
#define E(x)        return writeln(x),0
#define LL			(long long)
#define p(x)        printf("~%lld~\n",LL(x))
#define pp(x,y)     printf("~~%lld %lld~~\n",LL(x),LL(y))
#define ppp(x,y,z)  printf("~~~%lld %lld %lld~~~\n",LL(x),LL(y),LL(z))
#define pppp(a,b,c,d)	printf("~~~%lld %lld %lld %lld\n",LL(a),LL(b),LL(c),LL(d))
#define f_in(x)     freopen(x".in","r",stdin)
#define f_out(x)    freopen(x".out","w",stdout)
#define open(x)     f_in(x),f_out(x)
#define fi first
#define se second
#define GuYue		puts("\nGuYueNa________________________________________________________________________________")
typedef complex<double> E;
namespace SHENZHEBEI{
#ifdef LOCAL
    struct _{_(){freopen("cf.in","r",stdin);}}_; 
#endif 
#define NEG 1
    static const int GYN=2333333;
    char SZB[GYN],*SS=SZB,*TT=SZB;
    inline char gc(){   if (SS==TT){  TT=(SS=SZB)+fread(SZB,1,GYN,stdin); if (SS==TT) return '\n';  }   return *SS++;    }
#if NEG
    inline ll read(){    ll x=0,g=1; char ch=gc();   for (;!isdigit(ch);ch=gc()) if (ch=='-') g=-1;  for (;isdigit(ch);ch=gc())  x=x*10-48+ch;   return x*g; }
    inline void write(ll x){    if (x<0) putchar('-'),x=-x;  if (x>=10)   write(x/10);    putchar(x%10+'0');  }
#else
    inline ll read(){    ll x=0; char ch=gc();   for (;!isdigit(ch);ch=gc());    for (;isdigit(ch);ch=gc())  x=x*10-48+ch;   return x;   }
    inline void write(ll x){    if (x>=10)   write(x/10);    putchar(x%10+'0');  }
#endif
    inline char readchar(){ char ch=gc();   for(;isspace(ch);ch=gc());  return ch;  }
    inline ll readstr(char *s){ char ch=gc();   int cur=0;  for(;isspace(ch);ch=gc());      for(;!isspace(ch);ch=gc())  s[cur++]=ch;    s[cur]='\0';    return cur; }
	void Print(long long *a,int s,int t){For(i,s,t)printf("%lld ",a[i]);}
	void Print(int *a,int s,int t){For(i,s,t)printf("%d ",a[i]);}
	void Print(char *a,int s,int t){For(i,s,t)putchar(a[i]);}
	void writeln(ll x){write(x);puts("");}
}using namespace SHENZHEBEI;
const ll G=4,N=100010,mod=1e9+7;
ll a[N],sum,n;
struct dt{
	ll m[G][G];
	void clear(){memset(m,0,sizeof m);}
	void Print(){
		rep(i,0,G){
			rep(j,0,G)write(m[i][j]),putchar(' ');puts("");
		}
	}
}tmp,st,zy,Zy;
dt operator *(dt a,dt b){
	tmp.clear();
	rep(i,0,G)rep(j,0,G)rep(k,0,G)
	Add(tmp.m[i][j],a.m[i][k]*b.m[k][j]);
	return tmp;
}
void doit(ll k){
	dt	cogito=zy;
	for(;k;k>>=1){
		if (k&1)st=st*cogito;
		cogito=cogito*cogito;
	}
}
int main(){
	st.m[0][0]=1;
	sum=read();n=read();
	For(i,1,n)a[i]=read()+1;
	sort(a+1,a+n+1);
	zy.m[0][1]=2;zy.m[0][2]=1;
	zy.m[1][2]=1;zy.m[2][0]=1;zy.m[2][2]=1;
	zy.m[0][0]++;	zy.m[1][1]++;	zy.m[2][2]++;	zy.m[2][1]=2;
	Zy=zy;
	Zy.m[2][0]--;
	Zy.m[2][1]--;
	Zy.m[2][1]--;
	Zy.m[2][2]--;
	For(i,1,n){
		ll cishu=a[i]-a[i-1]-1;
		doit(cishu);
		st=st*Zy;
	}
	doit(sum-a[n]);
	writeln(st.m[0][2]);
}
/*
1	放0,1的板子
2	放1,2的板子
*/

Measured memory_bytes: 2048