#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

void chmin(long long &x, long long y) {
	x = min(x, y);
}

int main() {
	int n;
	cin >> n;
	vector<long long> a(n + 1);
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}

	static long long dp[2020][2020][2];
	const long long inf = 1e18;
	fill_n(**dp, 2020 * 2020 * 2, inf);

	dp[2][n][0] = a[1];
	dp[1][n - 1][1] = a[n];
	for (int d = n - 2; d >= 0; d--) {
		for (int l = 1; l + d <= n; l++) {
			int r = l + d;
			chmin(dp[l + 1][r][0], max<long long>(l - (l - 1), a[l] - dp[l][r][0]) + dp[l][r][0]);
			chmin(dp[l][r - 1][1], max<long long>(r - (l - 1), a[r] - dp[l][r][0]) + dp[l][r][0]);
			chmin(dp[l + 1][r][0], max<long long>((r + 1) - l, a[l] - dp[l][r][1]) + dp[l][r][1]);
			chmin(dp[l][r - 1][1], max<long long>((r + 1) - r, a[r] - dp[l][r][1]) + dp[l][r][1]);
		}
	}

	long long ans = 1e18;
	for (int i = 1; i <= n + 1; i++) {
		chmin(ans, dp[i][i - 1][0]);
		chmin(ans, dp[i][i - 1][1]);
	}
	cout << ans << endl;
}