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

// Problem: E. Clear the Multiset
// Contest: Codeforces - Educational Codeforces Round 94 (Rated for Div. 2)
// URL: http://codeforces.com/problemset/problem/1400/E
// Memory Limit: 256 MB
// Time Limit: 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

import java.io.*;
import java.util.*;

public class Main {
    private static PrintWriter pw = new PrintWriter(System.out);
    private static InputReader sc = new InputReader();

    static class InputReader{
        private static BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
        private static StringTokenizer tk;

        private void next()throws IOException{
            while(tk == null || !tk.hasMoreTokens())   
                tk = new StringTokenizer(r.readLine());
        }

        private int nextInt()throws IOException{
            next();
            return Integer.parseInt(tk.nextToken());
        }

        private int[] intArray(int n)throws IOException{
            next();
            int arr[] = new int[n];

            for(int i=0; i<n; i++)
                arr[i] = nextInt();

            return arr;
        }
    }
    
    private static int input[];
    
    private static long dp(int i, int j){
    	if(i > j)	return 0;
    	
    	int min = Integer.MAX_VALUE;
    	
    	for(int ptr = i; ptr <= j; ptr++)
    		min = Math.min(min, input[ptr]);
    	
    	long ans = min;
    	int begin = i;
    	
    	for(int ptr = i; ptr <= j; ptr++){
    		input[ptr] -= min;
    		
    		if(input[ptr] == 0){
    			ans += dp(begin, ptr - 1);
    			begin = ptr + 1;
    		}
    	}
    	
    	ans += dp(begin, j);
    	
    	ans = Math.min(ans, j - i + 1);
    	
    	return ans;
    }

    public static void main(String args[])throws IOException{
        int t = 1;
        while(t-->0)    solve();
        pw.flush();
        pw.close();
    }

    private static void solve()throws IOException{
		int n = sc.nextInt();
		input = sc.intArray(n);
		
		pw.println(dp(0, n - 1));
    }
}