#include <bits/stdc++.h>
#define REP_(i, a_, b_, a, b, ...) for (int i = (a), END_##i = (b); i < END_##i; ++i)
#define REP(i, ...) REP_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define ALL(x) std::begin(x), std::end(x)
using Int = long long;
using Uint = unsigned long long;
using Real = long double;
#include <atcoder/modint>
using Mint = atcoder::modint1000000007;
std::ostream &operator<<(std::ostream &os, const Mint &m) {
  return os << m.val();
}

template<typename T, typename U>
inline bool chmax(T &a, U b) { return a < b and ((a = b), true); }
template<typename T, typename U>
inline bool chmin(T &a, U b) { return a > b and ((a = b), true); }
template<typename T>
inline int ssize(const T &a) { return (int) a.size(); }
template<typename T>
constexpr T kBigVal = std::numeric_limits<T>::max() / 2;

struct Void {};

template<typename T>
inline std::ostream &print_one(const T &x, char endc) {
  if constexpr (std::is_same<T, Void>::value) {
    return std::cout;  // print nothing
  } else if constexpr (std::is_same<T, bool>::value) {
    return std::cout << (x ? "Yes" : "No") << endc;
  } else {
    return std::cout << x << endc;
  }
}
template<typename T>
inline std::ostream &print(const T &x) { return print_one(x, '\n'); }
template<typename T, typename... Ts>
std::ostream &print(const T &head, Ts... tail) {
  return print_one(head, ' '), print(tail...);
}
inline std::ostream &print() { return std::cout << '\n'; }

template<typename Container>
std::ostream &print_seq(const Container &seq,
                        const char *sep = " ",
                        const char *ends = "\n",
                        std::ostream &os = std::cout) {
  const auto itl = std::begin(seq), itr = std::end(seq);
  for (auto it = itl; it != itr; ++it) {
    if (it != itl) os << sep;
    os << *it;
  }
  return os << ends;
}

struct CastInput {
  template<typename T>
  operator T() const {
    T x;
    std::cin >> x;
    return x;
  }
  struct Sized {
    int n;
    template<typename T>
    operator T() const {
      T xs(n);
      for (auto &x: xs) std::cin >> x;
      return xs;
    }
  };
  Sized operator()(int n) const { return {n}; }
} in;

#ifdef MY_DEBUG
#include "debug_dump.hpp"
#include "backward.hpp"
backward::SignalHandling kSignalHandling;
#else
#define DUMP(...)
#define cerr if(false)cerr
#endif

using namespace std;

template<class T = Mint>
struct Factorials {
  // factorials and inverse factorials.
  std::vector<T> fact, ifact;

  // n: max cached value.
  explicit Factorials(int n) : fact(n + 1), ifact(n + 1) {
    assert(n >= 0);
    assert(n < T::mod());
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) {
      fact[i] = fact[i - 1] * i;
    }
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) {
      ifact[i - 1] = ifact[i] * i;
    }
  }
};

auto solve() {
  int n = in;
  vector<int> a = in(n);
  vector<int> freq(5005);
  for (auto x: a) ++freq[x];
  auto dp = vector(2, vector(n + 1, Mint(0)));
  dp[0][0] = 1;
  for (int i = 1; i <= n; ++i) {
    int i1 = (i & 1), i0 = i1 ^ 1;
    dp[i1] = dp[i0];
    for (int j = 1; j <= n; ++j) {
      dp[i1][j] += dp[i0][j - 1] * freq[i - 1];
    }
  }
  Factorials fs(n + 5);
  Mint ans = 0;
  for (int i = 0; i <= n; ++i) {
    int sign = (i & 1) ? -1 : 1;
    ans += sign * dp[n & 1][i] * fs.fact[n - i];
  }
  return ans;
}

int main() {
  std::ios::sync_with_stdio(false), cin.tie(nullptr);
  cout << std::fixed << std::setprecision(18);
  const int T = 1;//in;
  REP(t, T) {
    auto ans = solve();
    print(ans);
  }
}