#include <bits/stdc++.h>
using namespace std;
const int mod(1000007);
int sir[10001] , combinari[101][101] , stirling[101][101] , factorial[101] , putere[101];
bool gasit[10001];
int main ()
{
ios :: sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int lungime;
cin >> lungime;
combinari[0][0] = stirling[0][0] = factorial[0] = putere[0] = 1;
for (int total = 1 ; total <= lungime ; total++)
{
combinari[total][0] = 1;
putere[total] = 2LL * putere[total - 1] % mod;
factorial[total] = 1LL * factorial[total - 1] * total % mod;
for (int componente = 1 ; componente <= total ; componente++)
{
combinari[total][componente] = (combinari[total - 1][componente - 1] + combinari[total - 1][componente]) % mod;
stirling[total][componente] = (stirling[total - 1][componente - 1] + 1LL * stirling[total - 1][componente] * componente) % mod;
}
}
int rezultat = 1;
for (int indice = 1 , maxim = 0 , luat = 0 ; indice <= lungime ; indice++)
{
int valoare;
cin >> valoare;
for (int dat = 1 ; dat < valoare ; dat++)
{
int factor = 0;
const int ramas = max(dat , maxim) - luat - (gasit[dat] ? 0 : 1);
for (int total = ramas ; total <= lungime - indice ; total++)
{
if (total - ramas <= luat + (gasit[dat] ? 0 : 1)) {
if ((factor += combinari[luat + (gasit[dat] ? 0 : 1)][total - ramas]) >= mod)
{ factor -= mod; }
}
if ((rezultat += 1LL * stirling[lungime - indice][total] * factorial[total] % mod * factor % mod) >= mod)
{ rezultat -= mod; }
}
}
if (!gasit[valoare])
{
maxim = max(maxim , valoare);
gasit[valoare] = true;
luat++;
}
}
cout << rezultat;
return 0;
}
