#include <cstdio>
#include <vector>
#include <climits>
#include <cstring>
#include <algorithm>
using namespace std;

#define N 30
int n;
int as[N],ids[N];
int vss[N][N];

int lis(int* vs) {
	for (int i=0;i<n;++i) as[i]=INT_MAX;
  for (int i=0;i<n;++i) {
    ids[i]=lower_bound(as,as+n,vs[i])-as;
    as[ids[i]]=vs[i];
  }
  int m=*max_element(ids,ids+n);
  return m+1;
}

int solve(int* vs, int step, int ub) {
  int k=lis(vs);
	if (step+n-k>ub) return 0;
  if (step>ub) return 0;
  if (k==n) return 1;

  int fr=0,to=n-1;
  while(vs[fr]==fr) ++fr;
  while(vs[to]==to) --to;

	int* nvs=vss[step+1];
  for (int i=fr;i<=to;++i) {
    int v=vs[i];
		memcpy(vss[step+1],vss[step],sizeof(vss[step]));
    if (i<v) {
      for (int j=i+1;j<=v;++j) nvs[j-1]=vs[j];
    } else {
      for (int j=i-1;j>=v;--j) nvs[j+1]=vs[j];
    }
		nvs[v]=v;
    if (solve(nvs,step+1,ub)) return 1;
  }
  return 0;
}

int main() {
  scanf("%d",&n);
	for (int i=0;i<n;++i) scanf("%d",&vss[0][i]),--vss[0][i];
	for (int ans=0;;++ans) {
		if (solve(vss[0],0,ans))  {
			printf("%d\n",ans);
			break;
		}
	}
}