/* -*- coding: utf-8 -*-
 *
 * 663.cc: No.663 セルオートマトンの逆操作 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 2000;
const long long MOD = 1000000007;

const bool rls[4][4][2] = {
  {{1, 0}, {0, 1}, {0, 0}, {0, 0}}, // 000, 001, ---, ---
  {{0, 0}, {0, 0}, {0, 1}, {0, 1}}, // ---, ---, 010, 011
  {{1, 0}, {0, 1}, {0, 0}, {0, 0}}, // 100, 101, ---, ---
  {{0, 0}, {0, 0}, {0, 1}, {1, 0}}, // ---, ---, 110, 111
};

/* typedef */

typedef long long ll;

/* global variables */

int es[MAX_N];
ll dp[MAX_N + 1][4][4];

/* subroutines */

inline void addmod(ll &a, ll b) { a = (a + b) % MOD; }

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &es[i]);

  for (int k = 0; k < 4; k++) dp[0][k][k] = 1;

  for (int i = 0; i < n; i++)
    for (int j = 0; j < 4; j++)
      for (int k = 0; k < 4; k++)
	if (dp[i][j][k] > 0)
	  for (int l = 0; l < 4; l++)
	    if (rls[k][l][es[i]])
	      addmod(dp[i + 1][j][l], dp[i][j][k]);

  ll sum = 0;
  for (int k = 0; k < 4; k++)
    addmod(sum, dp[n][k][k]);

  printf("%lld\n", sum);
  return 0;
}