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 <vector>
#include <algorithm>

using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> h;
    for (int i = 0; i < N; i++) {
        int hi;
        cin >> hi;
        h.push_back(hi);
    }
    h.push_back(0);

    int count = 0;
    while (*max_element(h.begin(), h.end()) > 0){
        int prev = h.at(0);
        for (int i = 1; i < N + 1; i++) {
            if (prev > 0 && h.at(i) <= 0) {
                count++;
            }
            prev = h.at(i);
        }
        for (int i = 0; i < N; i++) {
            h[i]--;
        }
    }
    cout << count << endl;
    return 0;
}