// Is it a wonder I broke? Let's hear one more joke
// Then we could all just laugh until I cry
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <bitset>
typedef long long ll;
using namespace std;
const int maxn = 305;
int dp[maxn][maxn][maxn]; // interval co ostava, zaciatok hodnot, max pocet tych co si mozeme nechat
void upd(int& a, int b) { a = max(a, b); }
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vector<int> p(n);
for (int i = 0; i < n; i++) cin >> p[i], p[i]--;
int ans = 0;
for (int l = 0; l < n; l++) for (int r = n - 1; r >= l; r--)
{
for (int vl = 0; vl + (r - l) < n; vl++)
{
int vr = vl + r - l;
if (l == r)
{
if (p[l] == vr) upd(ans, dp[l][r][vl] + 1);
upd(ans, dp[l][r][vl]);
continue;
}
upd(dp[l + 1][r][vl + 1], dp[l][r][vl] + (p[l] == vl));
upd(dp[l][r - 1][vl + 1], dp[l][r][vl] + (p[r] == vl));
upd(dp[l + 1][r][vl], dp[l][r][vl] + (p[l] == vr));
upd(dp[l][r - 1][vl], dp[l][r][vl] + (p[r] == vr));
}
}
cout << n - ans << "\n";
return 0;
}
