#include <bits/stdc++.h>
#define int long long
#define ll long long
using ull = unsigned long long;
using namespace std;
const int INF = 1e10;
const int MOD = 1e9 + 7;
#define dump(x)                             \
    if (dbg) {                              \
        cout << #x << " = " << (x) << endl; \
    }
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORR(i, a, b) for (int i = (a); i <= (b); ++i)
#define pb push_back
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
#define all(v) (v).begin(), (v).end()
#define SZ(x) ((int)(x).size())
#define P pair<int, int>
#define V vector<int>
#define itn int
bool dbg = false;
int N;
int A[101010];

//Template by yosupo
template <uint MD>
struct ModInt {
    using M = ModInt;
    const static M G;
    uint v;
    ModInt(ll _v = 0) { set_v(_v % MD + MD); }
    M& set_v(uint _v) {
        v = (_v < MD) ? _v : _v - MD;
        return *this;
    }
    explicit operator bool() const { return v != 0; }
    M operator-() const { return M() - *this; }
    M operator+(const M& r) const { return M().set_v(v + r.v); }
    M operator-(const M& r) const { return M().set_v(v + MD - r.v); }
    M operator*(const M& r) const { return M().set_v(ull(v) * r.v % MD); }
    M operator/(const M& r) const { return *this * r.inv(); }
    M& operator+=(const M& r) { return *this = *this + r; }
    M& operator-=(const M& r) { return *this = *this - r; }
    M& operator*=(const M& r) { return *this = *this * r; }
    M& operator/=(const M& r) { return *this = *this / r; }
    bool operator==(const M& r) const { return v == r.v; }
    M pow(ll n) const {
        M x = *this, r = 1;
        while (n) {
            if (n & 1)
                r *= x;
            x *= x;
            n >>= 1;
        }
        return r;
    }
    M inv() const { return pow(MD - 2); }
    friend ostream& operator<<(ostream& os, const M& r) { return os << r.v; }
};
using Mint = ModInt<MOD>;

//Template by yosupo
const int MN = 1'000'000;
Mint fact[MN], iFac[MN];

void first() {
    fact[0] = Mint(1);
    for (int i = 1; i < MN; i++)
        fact[i] = fact[i - 1] * Mint(i);
    iFac[MN - 1] = fact[MN - 1].inv();
    for (int i = MN - 1; i >= 1; i--) {
        iFac[i - 1] = iFac[i] * Mint(i);
    }
    assert(fact[2345] * iFac[2345] == Mint(1));
}
Mint C(int n, int k) {
    if (n < k || k < 0)
        return Mint(0);
    return fact[n] * iFac[k] * iFac[n - k];
}

void solve() {
    Mint ans = 1;
    int c = 0;
    //multiset<int> S;
    int a[10];
    FOR(i, 0, 3) {
        a[i] = -1;
    }
    FOR(i, 0, N) {
        itn t = A[i];
        if (t == 0) {
            c += 1;
            //S.insert(t);
            FOR(i, 0, 3) {
                if (a[i] == -1) {
                    a[i] = 0;
                    break;
                }
            }
        } else {
            int tmp = 0;
            FOR(i, 0, 3) {
                if (a[i] == t - 1)
                    tmp++;
            }
            //ans *= S.count(t - 1);
            ans *= tmp;
            FOR(i, 0, 3) {
                if (a[i] == t - 1) {
                    a[i]++;
                    break;
                }
            }
            //S.erase(S.find(t - 1));
            //S.insert(t);
        }
    }
    if (c == 1) {
        ans *= 3;
    } else if (c == 2) {
        ans *= 6;
    } else {
        ans *= 6;
    }
    if (c >= 4) {
        ans = 0;
    }
    cout << ans << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cin >> N;
    FOR(i, 0, N)
    cin >> A[i];
    solve();
    return 0;
}


Measured memory_bytes: 8960