#include <bits/stdc++.h>
#define int long long
using namespace std;
struct Fenwick
{
int N;
vector<int> BIT;
Fenwick(int n) : N(n+1), BIT(N) {}
void update(int iPos, int delta)
{
for (iPos++; iPos < N; iPos += iPos & -iPos)
BIT[iPos] += delta;
}
int sum(int r) // sum < r
{
int sol(0);
for (; r; r -= r * -r)
sol += BIT[r];
return sol;
}
int sum(int l, int r) // l <= i < r
{
return sum(r) - sum(l);
}
};
signed main(void)
{
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int nbElem;
cin >> nbElem;
vector<int> hauteurs(nbElem);
vector<int> positions(nbElem);
for (int iPos = 0; iPos < nbElem; ++iPos)
{
cin >> hauteurs[iPos];
--hauteurs[iPos];
positions[hauteurs[iPos]] = iPos;
}
Fenwick fen(nbElem+1);
for (int iPos = 0; iPos < nbElem; ++iPos)
fen.update(iPos, 1);
vector<int> dp(nbElem+1, 1e18);
dp[0] = 0;
for (int dejaPlace(0); dejaPlace < nbElem; ++dejaPlace)
{
for (int placeApres(1); placeApres + dejaPlace <= nbElem; ++placeApres)
{
int coutPlacement = dp[dejaPlace];
for (int iPos = dejaPlace; iPos < dejaPlace+placeApres; ++iPos)
for (int j(0); j < positions[iPos]; ++j)
if (hauteurs[j] >= dejaPlace and (hauteurs[j] >= dejaPlace + placeApres or hauteurs[j] < iPos))
++coutPlacement;
dp[dejaPlace+placeApres] = min(dp[dejaPlace+placeApres], coutPlacement);
}
}
cout << dp[nbElem] << endl;
}
