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.util.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;

class Main{
    public static void main(String[] args){
        
        Scanner sc = new Scanner(System.in);
        
        int N = sc.nextInt();
        int[] h = new int[N + 1];

        for(int i=0; i<N; i++){
            h[i] = sc.nextInt();
        }

        h[N] = 0;

        int ans = 0;
        int sum = 0;
        for(int i=0; i<=100; i++){
            for(int j=0; j<=N; j++){
                if(j>0 && h[j]==0 && h[j-1]!=0){
                    sum++;
                }
            }
            for(int j=0; j<=N; j++){
                if(h[j]!=0){
                    h[j]--;
                }
            }
            ans += sum;
            sum = 0;
        }
        System.out.println(ans);
    }
}