// tested by Hightail: https://github.com/dj3500/hightail #include <iostream> #include <cstdio> #include <string> #include <vector> #include <set> #include <map> #include <queue> #include <cmath> #include <algorithm> #include <sstream> #include <stack> #include <cstring> #include <iomanip> #include <ctime> #include <cassert> using namespace std; #define pb push_back #define INF 1001001001 #define FOR(i,n) for(int (i)=0;(i)<(n);++(i)) #define FORI(i,n) for(int (i)=1;(i)<=(n);++(i)) #define mp make_pair #define pii pair<int,int> #define ll long long #define vi vector<int> #define SZ(x) ((int)((x).size())) #define fi first #define se second #define wez(n) int (n); scanf("%d",&(n)); #define wez2(n,m) int (n),(m); scanf("%d %d",&(n),&(m)); #define wez3(n,m,k) int (n),(m),(k); scanf("%d %d %d",&(n),&(m),&(k)); inline void pisz(int n) { printf("%d\n",n); } template<typename T,typename TT> ostream& operator<<(ostream &s,pair<T,TT> t) {return s<<"("<<t.first<<","<<t.second<<")";} template<typename T> ostream& operator<<(ostream &s,vector<T> t){FOR(i,SZ(t))s<<t[i]<<" ";return s; } #define DBG(vari) cout<<"["<<__LINE__<<"] "<<#vari<<" = "<<(vari)<<endl; #define ALL(t) t.begin(),t.end() #define FOREACH(i,t) for (__typeof(t.begin()) i=t.begin(); i!=t.end(); i++) #define TESTS wez(testow)while(testow--) #define REP(i,a,b) for(int (i)=(a);(i)<=(b);++i) #define REPD(i,a,b) for(int (i)=(a); (i)>=(b);--i) #define REMAX(a,b) (a)=max((a),(b)); #define REMIN(a,b) (a)=min((a),(b)); #define IOS ios_base::sync_with_stdio(0); const int N = 2405, mod = 1000000007; ll fact[N], inv[N], invfact[N]; // prepares inv[1..N-1], fact[0..N-1], invfact[0..N-1] void initnewton () { inv[1] = 1; REP(i,2,N-1) inv[i] = mod - mod / i * inv[mod % i] % mod; fact[0] = 1; REP(i,1,N-1) fact[i] = fact[i-1] * i % mod; invfact[0] = 1; REP(i,1,N-1) invfact[i] = invfact[i-1] * inv[i] % mod; } ll dp[N][N]; int tab[N]; int main () { initnewton(); wez(n) FORI(i,n) scanf("%d", tab+i); //FORI(i,n-1) if (tab[i] > tab[i+1]) cant[i] = 1; dp[0][n] = 1; REP(i,0,n-1) REP(a,1,n) if (dp[i][a] != 0) { dp[i][a] %= mod; for (int b = 1; i+b <= n && b <= a; ++b) { if (b >= 2 && tab[i+b-1] > tab[i+b]) break; ll th = dp[i][a] * fact[a] % mod * invfact[a-b] % mod; if (i == 0) th = dp[i][a];// * fact[b] % mod; dp[i+b][b] += th; } } ll res = 0; REP(a,1,n) res += dp[n][a] % mod; res = res % mod; if (res < 0) res += mod; cout << res; }