#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};
for(int i=0;i<=n;i++)
{
for(int j=0;j<=n;j++)
{
left[i][j]=1;
}
}
for(int i=0;i<=n;i++)dp[i]=1e9;
dp[0]=0;
for(int i=0;i<=n;i++)
{
// length of suffix fixed
// cout<<"For "<<i<<' '<<dp[i]<<endl;
for(int p=1;p<=n-i;p++)
{
int fe=n-i,le=p;
int sm=dp[i];
// for(int k=p;k<=n-i;k++)
for(int k=n-i;k>=p;k--)
{
// we place element fs at position k
// so we want suffix sum left[i][pos[fs]]
for(int ci=pos[le];ci<=n;ci++)
{
if(p<=a[ci] and a[ci]<=le)
{
// cost is set to zero
}
else
sm+=left[i][ci];
}
le++;
}
// p is the pos
// number fixed n-p+1
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;
}
