import java.io.*;
import java.util.*;


public class Main_yukicoder663 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		final int MOD = 1_000_000_007;

		int n = sc.nextInt();

		int[] e = new int[n];
		for (int i = 0; i < n; i++) {
			e[i] = sc.nextInt();
		}

		int[] mm = {0, 1, 1, 1, 0, 1, 1, 0};

		long ans = 0;
		for (int s = 0; s < 8; s++) {
			long[][] dp = new long[4][n];

			if (mm[s] != e[0]) {
				continue;
			}
			dp[s & 0x3][0] = 1;

			for (int i = 1; i < n; i++) {
				for (int j = 0; j < 8; j++) {
					if (mm[j] != e[i]) {
						continue;
					}

					dp[j & 0x3][i] += dp[j >> 1][i - 1];
					dp[j & 0x3][i] %= MOD;
				}
			}

			for (int i = 0; i < 4; i++) {
				if (i == s >> 1) {
					ans += dp[i][n - 1];
					ans %= MOD;
				}
			}
		}

		pr.println(ans);
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);

		solve();

		pr.close();
		sc.close();
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}