#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]=sum-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 2
    2 1
     
    1 1 1
    0	->	0	下一步放0个
    0	->	1	下一步放1个
    0	->	2	下一步放1个
    0	->	3	下一步放2个
    1	->	3	下一步放1个
    2	->	3	下一步放1个
    0	0	
    */

Measured memory_bytes: 2048