You have a multiset containing several integers. Initially, it contains a_1 elements equal to 1, a_2 elements equal to 2, ..., a_n elements equal to n.

You may apply two types of operations:

  * choose two integers l and r (l ≤ r), then remove one occurrence of l, one occurrence of l + 1, ..., one occurrence of r from the multiset. This operation can be applied only if each number from l to r occurs at least once in the multiset; 
  * choose two integers i and x (x ≥ 1), then remove x occurrences of i from the multiset. This operation can be applied only if the multiset contains at least x occurrences of i. 



What is the minimum number of operations required to delete all elements from the multiset?

Input

The first line contains one integer n (1 ≤ n ≤ 5000).

The second line contains n integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ 10^9).

Output

Print one integer — the minimum number of operations required to delete all elements from the multiset.

Examples

Input


4
1 4 1 1


Output


2


Input


5
1 0 1 0 1


Output


3
import java.util.*;
import java.io.*;
import java.math.BigInteger;

public class tr0 {
	static PrintWriter out;
	static StringBuilder sb;
	static int mod = 1000000007;
	static long inf = (long) 1e14;
	static int n, m, s1, s2;
	static ArrayList<Integer>[] ad;
	static long[][][] memo;
	static boolean f;
	static boolean vis[];
	static int[] sub;
	static int[] a;
	static long ans;
	static ArrayList<Long> ar;

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		out = new PrintWriter(System.out);
//		Random re=new Random();
//		n=re.nextInt(11)+3;
//		a=new int [n];
//		for(int i=0;i<n;i++)
//			a[i]=re.nextInt(11);
//		System.out.println(n);
//		System.out.println(Arrays.toString(a));
		n = sc.nextInt();
		a = sc.nextArrInt(n);
		out.println(cal(0, n - 1));
		out.flush();
	}

	static int cal(int l, int r) {
		int min = Integer.MAX_VALUE;
		for (int i = l; i <= r; i++)
			min = Math.min(min, a[i]);
		int ans = 0;
		ans += min;
		for (int i = l; i <= r; i++)
			a[i] -= min;
		int last = -1;
		for (int i = l; i <= r; i++) {
			if (a[i] == 0 && last != -1) {
				ans += cal(last, i - 1);
				last = -1;
			}
			if (a[i] > 0 && last == -1)
				last = i;
		}
		if (last != -1)
			ans += cal(last, r);
		return Math.min(ans, r - l + 1);
	}

	static class Scanner {
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream system) {
			br = new BufferedReader(new InputStreamReader(system));
		}

		public Scanner(String file) throws Exception {
			br = new BufferedReader(new FileReader(file));
		}

		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		public String nextLine() throws IOException {
			return br.readLine();
		}

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		public char nextChar() throws IOException {
			return next().charAt(0);
		}

		public Long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		public int[] nextArrInt(int n) throws IOException {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}

		public long[] nextArrLong(int n) throws IOException {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}

		public boolean ready() throws IOException {
			return br.ready();
		}

		public void waitForInput() throws InterruptedException {
			Thread.sleep(3000);
		}
	}
}
