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 <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin>>n;
  vector<int> h(n+2,0);
  for (size_t i = 1; i <= n; i++) {
    cin>>h[i];
  }
  vector<int> h2(1,0);
  bool age = 1;
  for (size_t i = 1; i <= n; i++) {
    if(age&&h[i+1]<h[i]){
      age=0;
      h2.push_back(h[i]);
    }
    if(!age&&h[i+1]>h[i]){
      age=1;
      h2.push_back(h[i]);
    }
  }
  h2.push_back(0);
  if(h2.size()==2){
    cout<<0;
    return 0;
  }
  int sum=0;
  for(int i=1;i<h2.size()-3;i+=2){
    sum+=max(h2[i]-h2[i-1],h2[i]-h2[i+1]);
  }
  sum+=h2[h2.size()-2]-h2[h2.size()-3];
  cout<<sum;
}