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 <bits/stdc++.h>

using namespace std;

#define int long long
#define MOD 1000000007

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i < (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define all(i) (i).begin(), (i).end()
#define rall(i) (i).begin(), (i).end(), greater<int>()

#define elif else if
#define eb emplace_back
#define pb push_back
#define mp make_pair
#define fst first
#define sec second
template <typename T>
void print(T x)
{
    std::cout << x << '\n';
}

//typedef long long ll;
#define TENNINE 1000000005
#define TENFIVE 100005
//#define int long long

int N;
vector<int> h;

signed main()
{

    cin >> N;
    h.resize(N);

    rep(i, N)
    {
        cin >> h[i];
    }

    int ans = 0;

    int flag = 1;

    while (1)
    {
        rep(i, N)
        {

            if (h[i] > 0)
            {
                h[i] -= 1;
                flag = 0;
            }
            else
            {
                if (flag == 0)
                {
                    ans++;
                }
                flag = 1;
            }

            if (i == N - 1)
            {
                if (flag == 0)
                {
                    ans++;
                }
                flag = 1;
            }
        }

        vector<int> temp;
        temp = h;

    
        sort(all(temp), greater<>());
        if (temp[0] == 0)
        {
            break;
        }
    }
    cout << ans << endl;

    return 0;
}