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 <string>
#include <algorithm>
#include <set>

int main()
{
    int N;
    std::cin >> N;
    std::vector<int> H(N), X(N);
    for (int i = 0; i < N; i++)
    {
        X[i] = 0;
        std::cin >> H[i];
    }

    int cnt = 0;
    while (true)
    {
        bool e = false;
        bool s = false;
        int a = 0;
        for (int i = 0; i < N; i++)
        {
            int x = X[i];
            if (x < H[i])
            {
                s = true;
            }
            else if (x == H[i])
            {
                a++;
                if (s) cnt++;
                s = false;
            }
            if (s)
            {
                X[i]++;
            }
        }
        if (s)cnt++;
        if (a == N)break;
    }

    std::cout << cnt << std::endl;


    return 0;
}