#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <unordered_map>
#include <unordered_set>
using namespace std;
template <int mod>
struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod) x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod) x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt &operator^=(long long p) {  // quick_pow here:3
    ModInt res = 1;
    for (; p; p >>= 1) {
      if (p & 1) res *= *this;
      *this *= *this;
    }
    return *this = res;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  ModInt operator^(long long p) const { return ModInt(*this) ^= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  explicit operator int() const { return x; }  // added by QCFium
  ModInt operator=(const int p) {
    x = p;
    return ModInt(*this);
  }  // added by QCFium
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      a -= t * b;
      std::swap(a, b);
      u -= t * v;
      std::swap(u, v);
    }
    return ModInt(u);
  }
  friend std::ostream &operator<<(std::ostream &os, const ModInt<mod> &p) {
    return os << p.x;
  }
  friend std::istream &operator>>(std::istream &is, ModInt<mod> &a) {
    long long x;
    is >> x;
    a = ModInt<mod>(x);
    return (is);
  }
};

struct Mo {
  int n;
  std::vector<std::pair<int, int>> lr;

  explicit Mo(int n) : n(n) {}

  void add(int l, int r) { /* [l, r) */
    lr.emplace_back(l, r);
  }

  template <typename AL, typename AR, typename EL, typename ER, typename O>
  void build(const AL &add_left, const AR &add_right, const EL &erase_left,
             const ER &erase_right, const O &out) {
    int q = (int)lr.size();
    int bs = n / std::min<int>(n, sqrt(q));
    std::vector<int> ord(q);
    std::iota(std::begin(ord), std::end(ord), 0);
    std::sort(std::begin(ord), std::end(ord), [&](int a, int b) {
      int ablock = lr[a].first / bs, bblock = lr[b].first / bs;
      if (ablock != bblock) return ablock < bblock;
      return (ablock & 1) ? lr[a].second > lr[b].second
                          : lr[a].second < lr[b].second;
    });
    int l = 0, r = 0;
    for (auto idx : ord) {
      while (l > lr[idx].first) add_left(--l);
      while (r < lr[idx].second) add_right(r++);
      while (l < lr[idx].first) erase_left(l++);
      while (r > lr[idx].second) erase_right(--r);
      out(idx);
    }
  }

  template <typename A, typename E, typename O>
  void build(const A &add, const E &erase, const O &out) {
    build(add, add, erase, erase, out);
  }
};
void solve() {
  using mint = ModInt<1000000007>;
  int n;
  std::cin >> n;
  bool haszero = false;
  bool great = false;
  std::vector<int> a(n);
  for (int x, i = 0; i < n; i++) {
    std::cin >> x;
    a[i] = x;
    if (!x) haszero = true;
    if (x > 3) great = true;
  }
  if (haszero) {
    std::cout << -1;
    return;
  }
  if (great) {
    std::cout << 1000000007 << '\n';
    return;
  }

  std::unordered_map<int, long long> mp;
  mp[1] = 1;
  mp[2] = 4;
  mp[3] = 729;
  long long ans = 1;
  long long modd = 1000000007;
  for (int i = 0; i < n; i++) {
    ans *= mp[a[i]];
    if (ans > modd) {
      std::cout << modd << '\n';
      return;
    }
  }
  std::cout << modd % ans << '\n';
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int t = 1;

  while (t--) solve();
  return 0;
}