#include <bits/stdc++.h>
using namespace std;
#define mp(a,b) make_pair(a,b)
#define ff first
#define setp setprecision(12)<<fixed
#define ss second
#define fori(v) for(int i=0; i<v; i++)
#define forj(v) for(int j=0; j<v; j++)
#define fork(v) for(int k=0; k<v; k++)
#define forl(v) for(int l=0; l<v; l++)
#define fort(v) for(int t=0; t<v; t++)
#define forz(v) for(int z=0; z<v; z++)
#define ll long long int
#define double long double
#define MAX (int)(pow(10,4)+ 10)
#define pb(a) push_back(a)
// #define cout out
// #define cin in
ll inf = pow(10,9);
ll modulo = 1000007;
double eps = 1e-10;
ifstream in;
ofstream out;
void deal(){
ll n;
cin>>n;
vector<ll> Mx(n);
vector<ll> arr(n);
fori(n)
cin>>arr[i];
Mx[0] = 0;
for(ll i = 1; i<n; i++)
Mx[i] = max(arr[i-1], Mx[i-1]);
vector<ll> dp(n+1, 1);
ll ans = 1;
for(ll i = n-1; i>-1; i--){
ans+=dp[Mx[i]] * (arr[i]-1);
ans%=modulo;
vector<ll> dpn(i+1,0);
for(ll j = 1; j<i+1; j++)
dpn[j] = (dp[j+1] + j*dp[j]) % modulo;
dp = dpn;
}
cout<<ans;
}
int main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
deal();
}
