#include <bits/stdc++.h>
#define FOR(i,x,n) for(int i=x; i<n; i++)
#define F0R(i,n) FOR(i,0,n)
#define ROF(i,x,n) for(int i=n-1; i>=x; i--)
#define R0F(i,n) ROF(i,0,n)
#define WTF cout << "WTF" << endl
#define IOS ios::sync_with_stdio(false); cin.tie(0)
#define F first
#define S second
#define pb push_back
#define ALL(x) x.begin(), x.end()
#define RALL(x) x.rbegin(), x.rend()
using namespace std;
typedef long long LL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef vector<int> VI;
typedef vector<LL> VLL;
typedef vector<PII> VPII;
typedef vector<PLL> VPLL;
const int MAXN = 1e4 + 7;
const int ALPHA = 27;
const int INF = 1e9 + 7;
const int MOD = 1e6 + 7;
const int LOG = 22;
using namespace std;
int ns[MAXN], mx[MAXN];
int dp[2][MAXN], n;
int main(){
IOS;
cin >> n;
FOR(i, 1, n + 1) {
cin >> ns[i];
mx[i] = max(mx[i - 1], ns[i]);
}
int ans = 1;
bool f = (n & 1);
f = 1 - f;
F0R(j, n + 1)
dp[f][j] = 1;
ROF(i, 1, n + 1) {
int d = (i & 1);
int g = 1ll * (ns[i] - 1) * dp[1 - d][ mx[i - 1] ] % MOD;
ans = (ans + g) % MOD;
F0R(j, i + 1)
dp[d][j] = (dp[1 - d][j + 1] + 1ll * dp[1 - d][j] * j % MOD) % MOD;
}
cout << ans % MOD;
}
