#include <bits/stdc++.h>
#define ll long long
#define s second
#define f first
#define pb push_back
#define pii pair <int,int>
#define left (h<<1),l,(l + r)/2
#define right ((h<<1)|1),(l + r)/2 + 1,r
#define int ll
using namespace std;
const int N = 2e5 + 3,inf = 1e18;
int a[N],dp[N],id[N],b[N],pr[N];
signed main() {
ios_base::sync_with_stdio(0),cin.tie(NULL),cout.tie(NULL);
int n;
cin>>n;
for (int i = 1; i <= n; i++)
cin >> a[i],dp[i] = inf,id[a[i]] = i;
//neli
for (int i = 1; i <= n; i++){
for (int k = 1; k <= i; k++){
int cost = 0;
for (int j = 1; j <= n; j++){
if (a[j] <= i - k) b[j] = 0;
else b[j] = 1;
}
for (int j = i; j >= i - k + 1; j--){
for (int w = 1; w < id[j]; w++)
cost += b[w];
b[id[j]] = 0;
}
dp[i] = min(dp[i],dp[i - k] + cost);
}
}
cout<<dp[n];
}
