就是最长上升子序列，但是要用n^2的算法。
#include<cstdio>
#include<algorithm>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;const int MAXN = 1123;
int a[MAXN], b1[MAXN], b2[MAXN], n;int main()
{scanf("%d", &n);REP(i, 0, n) scanf("%d", &a[i]);REP(i, 0, n){b1[i] = 1; //注意不能省！！ REP(j, 0, i)if(a[i] > a[j])b1[i] = max(b1[i], b1[j] + 1);}for(int i = n - 1; i >= 0; i--){b2[i] = 1; //不要忘！！ REP(j, i, n)if(a[i] > a[j])b2[i] = max(b2[i], b2[j] + 1);}int ans = 0;REP(i, 0, n)ans = max(ans, b1[i] + b2[i] - 1);printf("%d\n", n - ans);return 0;
}