#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
const int MOD = 1000007;
const ll INF = 1e18;
const int MX = 100001;
int n, x[10001], te[10001];
array<int,10001> dp, dp2;
int mul(int a, int b) { return (ll)a*b%MOD; }
int ad(int a, int b) { return (a+b)%MOD; }
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
FOR(i,1,n+1) {
cin >> x[i];
te[i] = max(x[i],te[i-1]);
}
int ans = 1;
FORd(i,1,n+1) {
if (i == n) {
F0R(i,n+1) dp[i] = 1;
} else {
F0R(j,i+1) dp[j] = ad(mul(j,dp2[j]),dp2[j+1]);
}
ans = ad(ans,mul(x[i]-1,dp[te[i-1]]));
swap(dp,dp2);
}
cout << ans;
}
// read the question correctly (is y a vowel? what are the exact constraints?)
// look out for SPECIAL CASES (n=1?) and overflow (ll vs int?)
