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.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for(int i=0;i<n;i++)h[i] = Integer.parseInt(sc.next());
        sc.close();
        int idx1,idx2;
        int min;
        int res = 0;
        while(true){
            idx1 = -1;
            min = 1000000;
            for(int i=0;i<n;i++){
                if(h[i]>0){
                    idx1 = i;
                    min = h[i];
                    break;
                }
            }
            if(idx1==-1)break;
            idx2 = n;
            for(int i=idx1+1;i<n;i++){
                if(h[i]==0){
                    idx2 = i;
                    break;
                }else{
                    min = Math.min(h[i],min);
                }
            }
            for(int i=idx1;i<idx2;i++){
                h[i]-=min;
            }
            res+=min;
        }
        System.out.println(res);
    }
}