#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

int es[2100], dp[2100][8];
const int MOD = 1e9 + 7;

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int N;
    std::cin >> N;

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

    int res = 0;
    for(int i=0;i<4;++i){
        memset(dp, 0, sizeof(dp));
        dp[1][i] = 1;
        for(int j=1;j<N;++j){
            for(int k=0;k<4;++k){
                if((110 >> (k * 2) & 1) == es[j]){
                    dp[j+1][k%2*2] = (dp[j+1][k%2*2] + dp[j][k]) % MOD;
                }
                if((110 >> (k * 2 + 1) & 1) == es[j]){
                    dp[j+1][k%2*2+1] = (dp[j+1][k%2*2+1] + dp[j][k]) % MOD;
                }
            }
        }

        for(int k=0;k<4;++k){
            if((k & 1) != (i >> 1)){
                continue;
            }
            if((110 >> ((k << 1) | i) & 1) == es[0]){
                res = (res + dp[N][k]) % MOD;
            }
        }
    }

    std::cout << res << std::endl;
}