#include<bits/stdc++.h>

using namespace std;
const int N = 1202;
const int Mod = 1000000007;
long long fact[N];
int main() {
	fact[0] = 1;
	for (int i = 1; i < 10; i++) {
		fact[i] = fact[i - 1] * i;
		fact[i] %= Mod;
	}
	int n;
	cin >> n;
	vector<int> v(n), vSorted(n);
	for (int i = 0; i < n; i++) {
		cin >> v[i];
		vSorted[i] = v[i];
	}
	sort(vSorted.begin(), vSorted.end());

	if (v == vSorted) {
		long long sum = 0;
		for (int i = 0; i < n; i++) {
			sum += fact[i];
			sum %= Mod;
		}
		cout << sum << endl;
	} else {
		cout << 1 << endl;
	}
}