Problem:
Score : 300 points

Problem Statement

In a flower bed, there are N flowers, numbered 1,2,......,N. Initially, the heights of all flowers are 0.
You are given a sequence h=\{h_1,h_2,h_3,......\} as input. You would like to change the height of Flower k to h_k for all k (1 \leq k \leq N), by repeating the following "watering" operation:

Specify integers l and r. Increase the height of Flower x by 1 for all x such that l \leq x \leq r.

Find the minimum number of watering operations required to satisfy the condition.

Constraints

1 \leq N \leq 100

0 \leq h_i \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
h_1 h_2 h_3 ...... h_N

Output

Print the minimum number of watering operations required to satisfy the condition.

Sample Input 1

4
1 2 2 1

Sample Output 1

2

The minimum number of watering operations required is 2.
One way to achieve it is:

Perform the operation with (l,r)=(1,3).

Perform the operation with (l,r)=(2,4).

Sample Input 2

5
3 1 2 3 1

Sample Output 2

5

Sample Input 3

8
4 23 75 0 23 96 50 100

Sample Output 3

221

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

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

public class Main {

	final static long MOD = 1000000007L;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static ArrayList<int[]> list = new ArrayList<>();
	public static long[] ans = new long[]{-1,-1,-1};
	public static void main(String[] args) throws Exception {


		int N=nextInt();

		int[] h = nextInts();
		int i=0;
		int ans = 0;
		while(i<h.length){
			int min=10101;
			for(int k=i;k<N;k++){
				if(h[k]==0){
					break;
				}
				min=Math.min(min, h[k]);
			}
			for(int k=i;k<N;k++){
				if(h[k]==0){
					break;
				}
				h[k]-=min;
			}
			if(min!=10101){
				ans+=min;
			}
			if(h[i]==0){
				i++;
				continue;
			}
		}
		System.out.println(ans);
	}

	public static String[] toStringArray(String s) {
		String[] tmp = new String[s.length()];
		char[] c = s.toCharArray();
		for (int i = 0; i < tmp.length; i++) {
			tmp[i] = String.valueOf(c[i]);
		}
		return tmp;
	}

	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}


}