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

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}
template<typename T>
vector<vector<T> > make_v(size_t a,size_t b){
  return vector<vector<T> >(a,make_v<T>(b));
}
template<typename T>
vector<vector<vector<T> > > make_v(size_t a,size_t b,size_t c){
  return vector<vector<vector<T> > > (a,make_v<T>(b,c));
}
template<typename T>
vector<vector<vector<vector<T> > > > make_v(size_t a,size_t b,size_t c,size_t d){
  return vector<vector<vector<vector<T> > > > (a,make_v<T>(b,c,d));
}

template<typename T>
vector<vector<vector<vector<vector<T> > > > > make_v(size_t a,size_t b,size_t c,size_t d,size_t e){
  return vector<vector<vector<vector<vector<T> > > > >(a,make_v<T>(b,c,d,e));
}

template<typename T,typename V>
typename enable_if<is_class<T>::value==0>::type
fill_v(T &t,const V &v){t=v;}

template<typename T,typename V>
typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t,const V &v){
  for(auto &e:t) fill_v(e,v);
}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<Int> e(n);
  for(Int i=0;i<n;i++) cin>>e[i];
  auto dp=make_v<Int>(2,2,2,2,n+1);
  fill_v(dp,0);
  for(Int a=0;a<2;a++)
    for(Int b=0;b<2;b++)
      dp[a][b][a][b][1]=1;
  auto calc=[](Int x,Int y,Int z){
    if(x==0&&y==0&&z==0) return 0;
    if(x==0&&y==0&&z==1) return 1;
    if(x==0&&y==1&&z==0) return 1;
    if(x==0&&y==1&&z==1) return 1;
    if(x==1&&y==0&&z==0) return 0;
    if(x==1&&y==0&&z==1) return 1;
    if(x==1&&y==1&&z==0) return 1;
    if(x==1&&y==1&&z==1) return 0;
    return 0;
  };
  Int ans=0;
  const Int MOD= 1e9+7;
  for(Int i=1;i<n;i++){
    for(Int a=0;a<2;a++){
      for(Int b=0;b<2;b++){
	for(Int c=0;c<2;c++){
	  for(Int d=0;d<2;d++){
	    for(Int x=0;x<2;x++){
	      if(calc(c,d,x)!=e[i]) continue;
	      if(i+1==n){
		if(x!=a||calc(d,a,b)!=e[0]) continue;
		//cout<<a<<" "<<b<<" "<<c<<" "<<d<<":"<<dp[a][b][c][d][i]<<endl;
		ans+=dp[a][b][c][d][i];
		ans%=MOD;
	      }else{
		dp[a][b][d][x][i+1]+=dp[a][b][c][d][i];
		dp[a][b][d][x][i+1]%=MOD;
	      }
	    }
	  }
	}
      }
    }
  }
  cout<<ans<<endl;
  return 0;
}