#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define minimize(a, x) a = std::min(a, x)
#define maximize(a, x) a = std::max(a, x)

typedef long long ll;
int const inf = 1<<29;

template<class value_type, int MOD>
class ModInt {
private:
  value_type val_;
  static value_type mod_pow(value_type x, value_type n, value_type mo) { value_type ret = 1; while(n > 0) { if(n & 1) { ret = ret * x % mo; } x = x * x % mo; n >>= 1; } return ret; }

public:

  ModInt() { val_ = 0; }
  ModInt(value_type x) { val_ = (x % MOD + MOD) % MOD; }

  ModInt const operator + (ModInt const& rhs) const {
    return std::move(ModInt(val_+rhs.get()));
  }

  ModInt const operator - (ModInt const& rhs) const {
    return std::move(ModInt(val_-rhs.get()));
  }

  ModInt const operator * (ModInt const& rhs) const {
    return std::move(ModInt(val_*rhs.get()));
  }

  ModInt const operator / (ModInt const& rhs) const {
    return std::move(ModInt(val_*mod_pow(rhs.get(), MOD-2, MOD)));  // fermat theorem
  }

  friend ModInt const operator + (value_type lhs, ModInt const& rhs) {
    return std::move(ModInt(lhs+rhs.get()));
  }

  friend ModInt const operator - (value_type lhs, ModInt const& rhs) {
    return std::move(ModInt(lhs-rhs.get()));
  }

  friend ModInt const operator * (value_type lhs, ModInt const& rhs) {
    return std::move(ModInt(lhs*rhs.get()));
  }

  friend ModInt const operator / (value_type lhs, ModInt const& rhs) {
    return std::move(ModInt(lhs*mod_pow(rhs.get(), MOD-2, MOD)));  // fermat theorem
  }

  ModInt operator += (ModInt const& rhs) {
    return *this = ModInt(val_+rhs.get()).get();
  }

  ModInt operator -= (ModInt const& rhs) {
    return *this = ModInt(val_-rhs.get()).get();
  }

  ModInt operator *= (ModInt const& rhs) {
    return *this = ModInt(val_*rhs.get()).get();
  }

  ModInt operator /= (ModInt const& rhs) {
    return *this = ModInt(val_*mod_pow(rhs.get(), MOD-2, MOD)).get();
  }

  bool operator == (ModInt const& rhs) const {
    return val_ == rhs.get();
  }

  value_type const get() const { return val_; }
  value_type &     get() { return val_; }

  friend ostream& operator << (ostream& ost, ModInt const& x) { 
    return ost << x.get();
  }

  friend istream& operator >> (istream& ist, ModInt& x) { 
    string s; ist >> s;
    int size = s.size();
    x.get() = 0;
    rep(i, size) {
      x.get() *= 10;
      x.get() += s[i]-'0';
      x.get() %= MOD;
    }
    return ist;
  }
};

typedef ModInt<long long, 1000000007> mint;


vector<mint> dp(5050);
vector<mint> P(5050);
int ngnums[5050];

int main() {

  int N; cin >> N;
  rep(i, N) { int a; cin >> a; ngnums[a]++; }

  dp[0] = 1;
  rep(i, N) for(int j=N-1; j>=0; j--)
    dp[j + 1] += dp[j] * ngnums[i]; // i1がダメな生徒 ∨ i2がダメな生徒　∨ ...

  P[0] = 1; REP(i, 1, N+1) P[i] = P[i-1] * i;

  mint ans = 0;

  // ダメな割当のない自由な割当 = 完全に自由な割当 - 1人だけダメな割当 + 2人だけダメな割当 - 3人だけダメな割当 + ... + (-1)^k k人ダメな割当 + ... (-1)^N N人ダメな割当

  rep(i, N+1) {
    ans += (i % 2 == 0 ? +1 : -1) * dp[i] * P[N - i];
  }

  cout << ans << endl;

  return 0;
}