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++ (GCC 9.2.1) (judge verdict: Accepted)

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

int main() {
  int N;
  cin >> N;
  vector<int> h(N),height(N,0);
  for(int i=0;i<N;i++) cin >> h.at(i);
  int ans = 0;
  while(1){
    int ans_tmp = ans;
    for(int i=0;i<N;i++){
      if(height.at(i) != h.at(i) ){
        for(int j=i;j<N;j++){
          if(height.at(j) != h.at(j) ) height.at(j) ++;
          else break;
        }
        ans ++;
        i = -1;
      }
    }
//    cout << ans << endl;
//    for(int k=0;k<N;k++) cout << height.at(k) << endl;
    if(ans == ans_tmp) break;
  }
  
//  for(int i=0;i<N;i++) cout << height.at(i) << endl;
  cout << ans << endl;
}