#include <bits/stdc++.h>

#ifdef DEBUG
#define PRINT(x)\
    cout<<"func "<<__func__<<": line "<<__LINE__<<": "<<#x<<" = "<<(x)<<endl;
#define PRINTA(a,first,last)\
    cout<<"func "<<__func__<<": line "<<__LINE__<<": "<<#a<<"["<<(first)<<", "<<(last)<<")"<<endl;\
    for (int i=(first);i<(last);++i){cout<<#a<<"["<<i<<"] = "<<(a)[i]<<endl;}
#define PRINTP(p)\
    cout<<"func "<<__func__<<": line "<<__LINE__<<": "<<#p<<" = ("<<(p.first)<<", "<<(p.second)<<")"<<endl;
#define PRINTI(a,i)\
    cout<<"func "<<__func__<<": line "<<__LINE__<<": "<<#a<<"["<<#i<<"] = "<<#a<<"["<<(i)<<"] = "<<(a)[i]<<endl;
#else
#define PRINT(x)
#define PRINTA(a,first,last)
#define PRINTP(p)
#define PRINTI(a,i)
#endif

#define FOR(i,a,b) for (int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);--i)
#define REP(i,n) for (int i=0;i<(n);++i)
#define RREP(i,n) for (int i=(n)-1;i>=0;--i)
#define pb push_back
#define mp make_pair
#define all(a) (a).begin(),(a).end()
#define MOD 1000000007

using namespace std;

using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;

template <class T, class U> void amax(T& x, U y) {if (x < y) x = y;}
template <class T, class U> void amin(T& x, U y) {if (x > y) x = y;}

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

template <class T, T M>
class modulo {
public:
    T data;

    modulo(T data = 0) : data(data % M) {
    }

    modulo operator+(const modulo &x) const {
        return modulo(data + x.data);
    }

    modulo operator-(const modulo &x) const {
        return modulo(data + (M - x.data));
    }

    modulo operator*(const modulo &x) const {
        return modulo(data * x.data);
    }

    modulo operator/(const modulo &x) const {
        return modulo(data * x.inv().data);
    }

    modulo operator+=(const modulo &x) {
        data = (data + x.data) % M;
    }

    modulo operator-=(const modulo &x) {
        data = (data + (M - x.data)) % M;
    }

    modulo operator*=(const modulo &x) {
        data = (data * x.data) % M;
    }

    modulo operator/=(const modulo &x) {
        data = (data * x.inv().data) % M;
    }

    modulo inv() const {
        return _pow(M - 2);
    }

    template <class Integer>
    modulo operator^(Integer n) const {
        if (n >= 0) {
            return _pow(n);
        } else {
            return _pow(M - 1 - (-n) % (M - 1));
        }
    }

    friend std::ostream& operator<<(std::ostream &os, const modulo &x) {
        os << x.data;
        return os;
    }

private:
    template <class NonNegativeInteger>
    modulo _pow(NonNegativeInteger n) const {
        modulo result(1);
        modulo x(*this);
        while (n) {
            if (n & 1) {
                result *= x;
            }
            x *= x;
            n >>= 1;
        }
        return result;
    }
};

using mod = modulo<ll, MOD>;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vector<int> A(N);
    REP(i, N) cin >> A[i];

    ll result = 1;
    vector<int> c(3, 0);
    REP(i, N) {
        int m = count(all(c), A[i]);
        result = (result * m) % MOD;
        REP(j, 3) {
            if (c[j] == A[i]) {
                ++c[j];
                break;
            }
        }
    }
    cout << result << endl;
    return 0;
}



Measured memory_bytes: 640