#include<bits/stdc++.h>

using namespace std;

typedef long long int64;
const int mod = 1e9 + 7;

int main() {
  int N, E[2000];

  cin >> N;
  for(int i = 0; i < N; i++) {
    cin >> E[i];
  }

  const int mask = (1 << 3) - 1;
  int beet[1 << 3] = {0, 1, 1, 1, 0, 1, 1, 0};
  vector< vector< int > > dp1(1 << 3, vector< int >(1 << 3));
  for(int j = 0; j < (1 << 3); j++) {
    if(E[1] == beet[j]) dp1[j][j] = 1;
  }
  for(int i = 2; i < N - 1; i++) {
    vector< vector< int > > dp2(1 << 3, vector< int >(1 << 3));
    for(int j = 0; j < (1 << 3); j++) {
      for(int k = 0; k < (1 << 3); k++) {
        int to = (k << 1) & mask;
        if(E[i] == beet[to]) { // うくくんね
          (dp2[j][to] += dp1[j][k]) %= mod;
        }
        to |= 1;
        if(E[i] == beet[to]) {
          (dp2[j][to] += dp1[j][k]) %= mod;
        }
      }
    }
    dp1.swap(dp2);
  }


  int ret = 0;
  for(int i = 0; i < (1 << 3); i++) {
    for(int j = 0; j < (1 << 3); j++) {
      auto bit = (j << 1) & mask;
      bit |= (i >> 2) & 1;
      if(E[N - 1] != beet[bit]) continue;
      bit <<= 1;
      bit &= mask;
      bit |= (i >> 1) & 1;
      if(E[0] != beet[bit]) continue;
      (ret += dp1[i][j]) %= mod;
    }
  }

  cout << ret << endl;
}