#include<iostream>
int n,m[3],i;main(){for(std::cin>>n;i<n;)std::cin>>m[i++];for(i=0;i++<*m;)*m%i+m[1]%i+m[2]%i||std::cout<<i<<"\n";}
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <queue>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>
#include <cctype>
#include <cmath>
#include <bitset>
#include <set>
#include <stack>
using namespace std;

#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,k,n) for(int i=(k);i<(int)(n);i++)
#define all(i,n) (i),(i+n)

int dx4[4]={1,0,-1,0};
int dy4[4]={0,-1,0,1};
int dx8[8]={1,0,-1,1,-1,1,0,-1};
int dy8[8]={1,1,1,0,0,-1,-1,-1};
int dx9[9]={0,1,0,-1,1,-1,1,0,-1};
int dy9[9]={0,1,1,1,0,0,-1,-1,-1};

typedef pair<int, int> P;
typedef pair<string, int> SP;
typedef long long ll;
typedef pair<ll, ll> PLL;

const int INF = 1e9;
const ll LLINF = 1e18;
const int MAX_V = 1e6+1;
const ll mod = 1000000007;
// << fixed << setprecision
// --------------------------------------
int n;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  cin >> n;

  ll ans = 1;
  int c[3];
  REP(i, 3) c[i] = 0;
  REP(i, n) {
    int a;
    cin >> a;
    int t = 0, p = 0;
    REP(j, 3) if(c[j] == a) {
      t++; p = j;
    }

    ans = (ans * t) % mod;
    c[p]++;
  }

  cout << ans << endl;
}
