https://www.luogu.org/problemnew/show/P1091

题解：先看从T1到Ti这一段单调递增的序列，再看Ti到TK这一段单调递减的序列，那么问题就解决了。先从1到n求一趟最长升，然后从n到1也求一趟，最后枚举中间的Ti，然后从众多Ti中挑个大的。

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
typedef __int128 lll;
const int N=10000;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int a[N];
int b[N];
int c[N];
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
    }
    b[0]=0;
    for(int i=1;i<=n;i++){
        for(int j=0;j<i;j++){
            if(a[i]>a[j])
                b[i]=max(b[i],b[j]+1);
        }
    }
    c[n+1]=0;
    for(int i=n;i>=1;i--){
        for(int j=n+1;j>i;j--){
            if(a[i]>a[j])
                c[i]=max(c[i],c[j]+1);
        }
    }
    int ans=0;
    for(int i=1;i<=n;i++){
        ans=max(ans,b[i]+c[i]-1);
    }
    cout << n-ans << endl;
    //cout << "Hello world!" << endl;
    return 0;
}