#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 1e4;
const int MOD = 1e6 + 7;
int v[MAX_N + 2], t[MAX_N + 2], dpCrt[MAX_N + 2], dpPrv[MAX_N + 2], ans[MAX_N + 1];
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> v[i];
    for (int i = 1; i <= n; i++) 
        t[i] = max(t[i - 1], v[i - 1]);
    for (int j = 1; j <= n; j++)
        dpPrv[j] = 1;
    for (int i = n; i >= 1; i--) {
        ans[i] = dpPrv[t[i]];
        for (int j = 1; j <= n; j++) 
            dpCrt[j] = ((long long)dpPrv[j] * j + dpPrv[j + 1]) % MOD;
        for (int j = 1; j <= n; j++)
            dpPrv[j] = dpCrt[j];
    }
    int day = 1;
    for (int i = 2; i <= n; i++)
        day = (day + (long long)(v[i] - 1) * ans[i]) % MOD;
    cout << day << "\n";
    
    return 0;
}
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