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 <iomanip>
#include <string>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <random>
#include <typeinfo>
#include <type_traits>

using namespace std;

template <typename T>	constexpr T	rep_start(const T &end)			{ return 0; }
template <typename T>	constexpr T	rep_start(const T &start, const T &end)	{ return start; }
template <typename T>	constexpr T	rep_end(const T &end)				{ return end; }
template <typename T>	constexpr T	rep_end(const T &start, const T &end)		{ return end; }

#define rep(index, ...) for (auto index = rep_start(__VA_ARGS__); index < rep_end(__VA_ARGS__); ++index)
#define irep(index, ...) for (auto index = rep_end(__VA_ARGS__) - 1; index >= rep_start(__VA_ARGS__); --index)

using llong = long long;
using ullong = unsigned long long;

int main ()
{
	int N;
	cin >> N;
	vector<int> h(N+1);
	h[0] = 0;
	rep(i, 1, N+1) cin >> h[i];

	int count = 0;
	rep(i, 1, N+1)
	{
		count += max(0, h[i] - h[i-1]);
	}

	cout << count << endl;

	return 0;
}