#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define all(x) x.begin(), x.end()
const int M = 10007;
const ll inf = 2e9;
const ll mod = 1e6 + 7;
const double pi = acos(-1);
const int dx[] = {0, -1, 0, 1}, dy[] = {1, 0, -1, 0};
const int block = 320;
ll n, a[M], pref[M], ans = 1;
vector <ll> dp(M), old(M);
ll getDp(int j){ return (dp[j] - dp[j - 1] + mod) % mod; }
ll getOld(int j){ return (old[j] - old[j - 1] + mod) % mod; }
int main(){
cin >> n;
for(int i = 1; i <= n; ++i) cin >> a[i], pref[i] = max(pref[i - 1], a[i]);
for(int i = n; i; --i){
for(ll j = 1; j <= i; ++j){
if(i == n) dp[j] = j;
else{
dp[j] = dp[j - 1];
dp[j] = (dp[j] + getOld(j + 1)) % mod;
dp[j] = (dp[j] + getOld(j) * j) % mod;
}
}
ll add = getDp(pref[i - 1]) * min(pref[i - 1], a[i] - 1);
if(a[i] > pref[i - 1]) add = (add + dp[a[i] - 1] - dp[pref[i - 1]] + mod) % mod;
ans = (ans + add) % mod;
swap(old, dp);
}
cout << ans << endl;
return 0;
}
