#include <iostream>
using namespace std;
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
int a[n+1],pos[n+1]={0};
for(int i=1;i<=n;i++)cin>>a[i],pos[a[i]]=i;
int dp[n+1]={0};
int left[n+1][n+1]={0};
int cst[n+1][n+1]={0};
int pre[n+2]={0};
int ppre[n+2]={0};
for(int i=0;i<=n;i++)
{
for(int j=0;j<=n;j++)
{
left[i][j]=1;
cst[i][j]=0;
}
}
for(int i=0;i<=n;i++)dp[i]=1e9;
dp[0]=0;
for(int l=1;l<=n;l++)
{
cst[l][l]=1;
for(int r=l+1;r<=n;r++)
{
cst[l][r]=cst[l][r-1];
for(int p=l;p<=r;p++)
{
cst[l][r]+=(pos[r]<=pos[p]);
}
}
}
for(int i=0;i<=n;i++)
{
// length of suffix fixed
// cout<<"For "<<i<<' '<<dp[i]<<endl;
for(int j=0;j<=n;j++)pre[j]=left[i][j];
for(int j=n-1;j>=0;j--)pre[j]+=pre[j+1];
for(int j=0;j<=n;j++)ppre[j]=pre[pos[j]];
for(int j=1;j<=n;j++)ppre[j]+=ppre[j-1];
for(int p=1;p<=n-i;p++)
{
int fe=n-i,le=p;
int sm=dp[i];
sm+=ppre[fe]-ppre[le-1]-cst[le][fe];
if(sm<dp[n-p+1])
{
dp[n-p+1]=sm;
for(int j=0;j<=n;j++)
{
if(p<=a[j] and a[j]<=n-i)
{
left[n-p+1][j]=0;
}
else{
left[n-p+1][j]=left[i][j];
}
}
}
}
}
cout<<dp[n]<<endl;
}
