#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e6+7;
ll dp[2][10004];
int arr[10001];
int pref_max[10002];
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random_start();
int n;
cin >> n;
rep2(i,1,n) cin >> arr[i];
rep2(i,1,n) pref_max[i] = max(pref_max[i-1],arr[i]);
ll ans = 0;
for(int i = n; i >= 1; i--)
{
if(i != n)
{
rep2(pop,1,arr[i]-1)
{
ans += dp[1][max(pref_max[i-1],pop)];
ans %= MOD;
}
rep2(j,1,n)
{
dp[0][j] = (dp[1][j]*j + dp[1][j+1]) % MOD;
}
rep2(j,1,n)
{
swap(dp[0][j],dp[1][j]);
dp[0][j] = 0;
}
}
else
{
rep2(j,1,n) dp[1][j] = j+1;
ans += (arr[i]-1);
ans %= MOD;
}
}
cout << (ans+1)%MOD << "\n";
}
