#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
long long int fact(int n){
    if(n==1){
        return 1;
    }
    return n*fact(n-1);
}
int main() {
    int n;
    cin>>n;
    int arr[n];
    cin>>arr[0];
    bool incr=false;
    for(int i=1;i<n;i++){
        cin>>arr[i];
        if(arr[i-1] > arr[i]){
            incr = true;
        }
    }
    if(incr) cout<<"1"<<endl;
    else cout<<fmod((double)(fact(n)-(n-1)), (double)(pow((double)10,(double)9)+7))<<endl;
    return 0;
}