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: Accepted)

#include <iostream>
#include <string>
#include <algorithm>
#include <map>
#include <vector>
#include <ctype.h>
#include <cmath>
#include <iomanip>
#include <ios>

using namespace std;

int main(void){
    
    int n;
    int ans=0;
    cin>>n;
    int h[n];
    for(int i=0;i<n;i++){
        cin>>h[i];
    }
    bool t=true;
    int sum=0;
    for(int i=0;i<n;i++){
        sum+=h[i];
        if(i==n-1&&sum==0){
            t=false;
        }
    }
    
    while(t){
        int l=1000,r=-1;
        for(int i=0;i<n;i++){
            //cout<<l<<' '<<r<<endl;
            if(h[i]>0&&i<l){
                l=i;
            }if(h[i]>0&&i>r){
                r=i;
            }if(l!=1000&&r!=-1&&h[i]==0){
                break;
            }if(i==n-1&&l==1000&&r==-1)t=false;
        }
        //cout<<endl;
        if(t){
            for(int i=l;i<=r;i++){
                h[i]-=1;
            }
            ans+=1;
        }
        
    }
    cout<<ans<<endl;
    
    return 0;
}