using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Math;

class MainClass : Scanner
{
    static void Main()
    {
        int N = RInt();
        var A = RInts();
        var dp = new long[N+1][];
        for (int i = 0; i < N+1; i++)
        {
            dp[i] = new long[3];
        }
        Modular ans = 1;
        for (int i = 0; i < N; i++)
        {
            ans *= dp[i].Count(_ => _ == A[i]);

            bool f = true;
            for (int j = 0; j < 3; j++)
            {
                if (f&&dp[i][j] == A[i])
                {
                    dp[i + 1][j] = dp[i][j] + 1;
                    f = false;
                }
                else
                {
                    dp[i + 1][j] = dp[i][j];
                }
            }

        }
        WriteLine((int)ans);
    }
}

class Modular
{
    private const int M = 1000000007;
    private long value;
    public Modular(long value = 0) { this.value = value; }
    public static implicit operator Modular(long a)
    {
        var m = a % M;
        return new Modular((m < 0) ? m + M : m);
    }
    public static Modular operator +(Modular a, Modular b)
    => a.value + b.value;
    public static Modular operator -(Modular a, Modular b)
    => a.value - b.value;
    public static Modular operator *(Modular a, Modular b)
    => a.value * b.value;
    public static Modular Pow(Modular a, int n)
    {
        switch (n)
        {
            case 0:
                return 1;
            case 1:
                return a;
            default:
                var p = Pow(a, n / 2);
                return p * p * Pow(a, n % 2);
        }
    }
    public static Modular operator /(Modular a, Modular b)
    {
        return a * Pow(b, M - 2);
    }
    private static readonly List<int> facs = new List<int> { 1 };
    public static Modular Fac(int n)   //階乗
    {
        for (int i = facs.Count; i <= n; ++i)
        {
            facs.Add((int)(Math.BigMul(facs.Last(), i) % M));
        }
        return facs[n];
    }
    public static Modular Fac(int r, int n)
    {
        int temp = 1;
        for (int i = r; i <= n; i++)
        {
            temp = (int)(Math.BigMul(temp, i) % M);
        }
        return temp;
    }
    public static Modular Ncr(int n, int r) //nCr
    {
        return (n < r) ? 0
             : (n == r) ? 1
                        : (n < 1000000) ? Fac(n) / (Fac(r) * Fac(n - r))
                            : Fac(n - r + 1, n) / Fac(r);
    }
    public static explicit operator int(Modular a)
    {
        return (int)a.value;
    }
}

class Scanner
{
    public static string RString() => Console.ReadLine();
    public static int RInt() => ReadTuple<int>();
    public static long RLong() => ReadTuple<long>();
    public static double RDouble() => ReadTuple<double>();

    public static string[] RStrings() => Console.ReadLine().Split();
    public static int[] RInts() => Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
    public static long[] RLongs() => Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
    public static double[] RDoubles() => Array.ConvertAll(Console.ReadLine().Split(), double.Parse);
    public static int[] RInts(Func<string, int> func) => Console.ReadLine().Split().Select(func).ToArray();
    public static long[] RLongs(Func<string, long> func) => Console.ReadLine().Split().Select(func).ToArray();
    public static double[] RDoubles(Func<string, double> func) => Console.ReadLine().Split().Select(func).ToArray();
    //public static string[] RStrings(Func<string, string> func) => Console.ReadLine().Split().Select(func).ToArray();

    public static T1 ReadTuple<T1>()
    {
        var r = RString();
        var r1 = (T1)Convert.ChangeType(r, typeof(T1));
        return r1;
    }
    public static (T1, T2) ReadTuple<T1, T2>()
    {
        var r = RStrings();
        var r1 = (T1)Convert.ChangeType(r[0], typeof(T1));
        var r2 = (T2)Convert.ChangeType(r[1], typeof(T2));
        return (r1, r2);
    }
    public static (T1, T2, T3) ReadTuple<T1, T2, T3>()
    {
        var r = RStrings();
        var r1 = (T1)Convert.ChangeType(r[0], typeof(T1));
        var r2 = (T2)Convert.ChangeType(r[1], typeof(T2));
        var r3 = (T3)Convert.ChangeType(r[2], typeof(T3));
        return (r1, r2, r3);
    }
    public static (T1, T2, T3, T4) ReadTuple<T1, T2, T3, T4>()
    {
        var r = RStrings();
        var r1 = (T1)Convert.ChangeType(r[0], typeof(T1));
        var r2 = (T2)Convert.ChangeType(r[1], typeof(T2));
        var r3 = (T3)Convert.ChangeType(r[2], typeof(T3));
        var r4 = (T4)Convert.ChangeType(r[3], typeof(T4));
        return (r1, r2, r3, r4);
    }
}


Measured memory_bytes: 44644