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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
using namespace std;

int main(){
    int n;
    cin >> n;

    int h[n];
    int zero_count_sum = 0;
    int area = 1;
    for (int i=0; i < n; i++){
        cin >> h[i];
    }

    for (int i=0; i < n; i++){
        if (h[i]==0){
            if (i==0 || h[i-1]==0 || h[i+1]==0 || i==n-1){
                zero_count_sum+=1;
            }else{
                zero_count_sum+=1;
                area+=1;
            }
        }
    }

    int ans = 0;
    int left_zero_pos = 0;
    int right_zero_pos = n-1;
    while (zero_count_sum<n){
//        cout << area  << ":";
        ans+=area;
        int new_zero = 0;
        for (int i=0; i<n; i++){
            if (h[i]>-1){
                h[i]-=1;
                if (h[i]==0){
                    if (h[i-1]<=0 && h[i+1]<=0){
                        area-=1;
                        zero_count_sum+=1;
                    }else if (i==0 || h[i-1]<=0 || h[i+1]<=0 || i==n-1){
                        zero_count_sum+=1;
                    }else{
                        new_zero+=1;
                    }
                }
            }
//            cout << h[i] << " ";
        }
        zero_count_sum+=new_zero;
        area+=new_zero;
//        cout << endl;
    }
    cout << ans << endl;
}