P3205 [HNOI2010]合唱队

/*
    区间DP,其中一种类型，
    转移分阶段性，且阶段性分两组
    i组，j组 
*/
#include <cmath>
#include <queue>
#include <cstdio>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>
#define ll long long
using namespace std;

const int A = 1e7+10;
const int B = 1e6+10;
const int mod = 19650827;
const int inf = 0x3f3f3f3f;

inline int read() {
  char c = getchar();
  int x = 0, f = 1;
  for ( ; !isdigit(c); c = getchar()) if (c == '-') f = -1;
  for ( ; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
  return x * f;
}

int f[2000][2000],g[2000][2000],n,a[B];

int main()
{
    int x;
    n=read();
    for (int i=1;i<=n;i++)
    {
        a[i]=read();
        f[i][i]=1;
        //g[i][i]=1;
    }
    
    for (int len=2;len<=n;len++)
        for (int i=1;i+len-1<=n;i++)
        {
            int j=i+len-1;
            f[i][j]=(f[i+1][j]*(a[i+1]>a[i])+g[i+1][j]*(a[i]<a[j]))%mod;
            g[i][j]=(f[i][j-1]*(a[j]>a[i])+g[i][j-1]*(a[j]>a[j-1]))%mod;
        }
    
    int ans=(f[1][n]+g[1][n])%mod;
    printf("%d",ans);
}