#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
using i64=long long;

template<typename T>
T fpow(T x,ll n)
{T res=1,a=x;while(n){if(n&1)res*=a;a*=a;n>>=1;}return res;}
const int P=1e9+7;
int norm(int x){
	if(x>=P){
		x-=P;
	}
	if(x<0){
		x+=P;
	}
	return x;
}
struct ModInt{
	int x;
	int val()const{return x;}
	ModInt(int _x=0):x(norm(_x)){}
	ModInt inv()const{return fpow(*this,P-2);}
	ModInt&operator+=(const ModInt&rhs){
		x=norm(x+rhs.x);
		return *this;
	}
	ModInt&operator-=(const ModInt&rhs){
		x=norm(x-rhs.x);
		return *this;
	}
	ModInt&operator*=(const ModInt&rhs){
		x=i64(x)*rhs.x%P;
		return *this;
	}
	ModInt&operator/=(const ModInt&rhs){
		return *this *=rhs.inv();
	}
	bool operator==(const ModInt&rhs)const{return x==rhs.x;}
	bool operator!=(const ModInt&rhs)const{return !(x==rhs.x);}
	bool operator==(const int rhs)const{return x==rhs;}
	bool operator!=(const int rhs)const{return !(x==rhs);}
	friend ModInt operator+(const ModInt&a,const ModInt&b){
		ModInt res=a;res+=b;
		return res;
	}
	friend ModInt operator-(const ModInt&a,const ModInt&b){
		ModInt res=a;res-=b;
		return res;
	}
	friend ModInt operator*(const ModInt&a,const ModInt&b){
		ModInt res=a;res*=b;
		return res;
	}
	friend ModInt operator/(const ModInt&a,const ModInt&b){
		ModInt res=a;res/=b;
		return res;
	}
	friend istream&operator>>(istream&is,ModInt&rhs){
		i64 v;is>>v;
		rhs=ModInt(v);
		return is;
	}
	friend ostream&operator<<(ostream&os,const ModInt&rhs){
		os<<rhs.val();
		return os;
	}
	ModInt sqrt();
};
using Z=ModInt;
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define drep(i,a,b) for(int i=a;i>=b;i--)


const int maxn=1010;
Z pw[maxn];
Z dp[2][80][80][80];
int t[maxn];
int n;
int cur;
Z ans;
int f[maxn][85];
int cover(int x,int y){
	if(f[x][y]) return f[x][y];
	int p=x-1;
	while(p+1<=n&&t[p+1]-t[x]+1<=y) p++;
	return f[x][y]=p-x+1;
}
int cover(int x,int y,int z){
	int tmp=cover(x,y);
	return tmp+cover(x+tmp,z);
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++) cin>>t[i];

    cur=1;
    ans=0;
    pw[0]=1;
    for(int i=1;i<maxn;i++) pw[i]=pw[i-1]*2;

	dp[0][0][cover(1,20)][cover(1,20,20)]=1;
    for(int i=1;i<=n;i++){
		// rep(a,0,75)rep(b,0,75)rep(c,0,75)
		// int tpa=cover(i,20),tpb=cover(i,20,20),tpc=max(tpb+cover(i,i+tpb,20),cover(i,75));
        // rep(a,0,tpc)rep(b,0,tpb)rep(c,0,tpc)
		// dp[cur][a][b][c]=0;
		memset(dp[cur],0,sizeof(dp[cur]));
        rep(a,0,75)rep(b,0,75)rep(c,0,75)
		{
            dp[cur][max(0,a-1)][max(0,b-1)][max(0,c-1)]+=dp[cur^1][a][b][c];

            if(a==0){
                ans+=pw[n-i]*dp[cur^1][a][b][c];
                int aa=max(cover(i,20)-1,b-1);
                int bb=max({cover(i,20,20)-1,aa+cover(i+aa+1,20),c-1});
                int cc=max({cover(i,75)-1,bb+cover(i+bb+1,20)});
                dp[cur][aa][bb][cc]+=dp[cur^1][a][b][c];
            }else{
				dp[cur][max(0,a-1)][max(0,b-1)][max(0,c-1)]+=dp[cur^1][a][b][c];
			}
        }
        cur^=1;
    }
    ans*=2;
    cout<<ans<<'\n';
    return 0;
}