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.io.*;
import java.lang.reflect.Array;
import java.util.*;

public class E {
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

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

        long nextLong() {
            return Long.parseLong(next());
        }

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

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

    static FastReader s = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);

    private static int[] rai(int n) {
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = s.nextInt();
        }
        return arr;
    }

    private static int[][] rai(int n, int m) {
        int[][] arr = new int[n][m];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                arr[i][j] = s.nextInt();
            }
        }
        return arr;
    }

    private static long[] ral(int n) {
        long[] arr = new long[n];
        for (int i = 0; i < n; i++) {
            arr[i] = s.nextLong();
        }
        return arr;
    }

    private static long[][] ral(int n, int m) {
        long[][] arr = new long[n][m];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                arr[i][j] = s.nextLong();
            }
        }
        return arr;
    }

    private static int ri() {
        return s.nextInt();
    }

    private static long rl() {
        return s.nextLong();
    }

    private static String rs() {
        return s.next();
    }

    static int gcd(int a, int b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }


    static int dfs(int[] arr,int l,int r)
    {
        if(l>r)
        {
            return 0;
        }
        int min=Integer.MAX_VALUE;
        for(int i=l;i<=r;i++)
        {
            min=Math.min(arr[i],min);
        }
        int curr=min;
        for(int i=l;i<=r;i++)
        {
            arr[i]-=min;
        }
        int newL=l;
        for(int i=l;i<=r;i++)
        {
            if(arr[i]==0)
            {
                curr+=dfs(arr,newL,i-1);
                newL=i+1;
            }
        }
        curr+=dfs(arr,newL,r);
//        System.out.println(curr);
        return Math.min(r-l+1,curr);
    }

    public static void main(String[] args) {
        StringBuilder ans = new StringBuilder();
//        int t = ri();
        int t = 1;
        while (t-- > 0) {
            int n=ri();
            int[] arr=rai(n);
            int max=Integer.MIN_VALUE;

            int l=0,r=n-1;
            int res=0;
            for(int i=0;i<n;i++)
            {
                if(arr[i]==0)
                {
                    res+=dfs(arr,l,i-1);
                    l=i+1;
                }
            }

            int val=dfs(arr,l,r);
//            System.out.println("val= "+val);
            res+=val;
            ans.append(res).append("\n");
        }
        out.print(ans.toString());
        out.flush();

    }


}


