#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef pair<ll, ll> pll; #define all(x) (x).begin(),(x).end() #define X first #define Y second #define sep ' ' #define endl '\n' #define debug(x) cerr << #x << ": " << x << endl; const ll MAXN = 1e4 + 10; const ll MOD = 1000007; int n, A[MAXN], mx[MAXN]; ll S[2][MAXN], ans; int main() { ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0); cin >> n; S[1][0] = 1; for (int i = 1; i <= n; i++) { cin >> A[i]; S[1][i] = i + 1; mx[i] = max(mx[i - 1], A[i]); } ans = A[n]; int ind = 1; for (int i = n - 1; i > 0; i--) { ind = ind ^ 1; for (int i = 0; i < MAXN - 1; i++) S[ind][i] = (S[ind ^ 1][i] * i + S[ind ^ 1][i + 1]) % MOD; ans = (ans + S[ind ^ 1][mx[i - 1]] * (A[i] - 1)) % MOD; } cout << ans << endl; return 0; }