#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

typedef bitset<2048> bit;

bit f(int n, bit x){
  bit ret;
  REP(i,n){
    int l = x[(i+n-1)%n];
    int m = x[i];
    int r = x[(i+1)%n];
    int y = (m+r+m*r+l*m*r)%2;
    if(y)ret.set(i);
  }
  return ret;
}

int n;
bit e;

ll dp[2521][4];
int rule[] = {0,1,1,1,0,1,1,0};

int main(){
  scanf("%d",&n);
  REP(i,n){
    int x;
    scanf("%d",&x);
    if(x)e.set(i);
  }
  ll ans = 0;
  REP(beg,8){
    if(rule[beg] != (int)e[0])continue;
    REP(i,2521)REP(j,4)dp[i][j]=0;
    dp[0][beg>>1] = 1;
    FOR(i,2,n-1){
      REP(j,4){
        REP(k,2){
          int msk = j + (k<<2);
          if(rule[msk] != (int)e[i-1])continue;
          dp[i-1][msk>>1] += dp[i-2][j];
          dp[i-1][msk>>1] %= MOD;
        }
      }
    }
    REP(j,4){
      int msk1 = j + ((beg&1)<<2);
      if(rule[msk1] != (int)e[n-2])continue;
      int msk2 = (j>>1) + ((beg&3)<<1);
      if(rule[msk2] != (int)e[n-1])continue;
      ans += dp[n-3][j];
      ans %= MOD;
    }
  }
  printf("%lld\n",ans);
  return 0;
}