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>
#define rep(i,n) for(int i = 0; i < n; i++)
using namespace std;
typedef long long ll;

const int MAX_N = 105;
int h[MAX_N];
bool A[MAX_N][MAX_N];

int main()
{
	for (int i = 0; i < MAX_N; ++i)
	{
		for (int j = 0; j < MAX_N; ++j)
		{
			A[i][j] = false;
		}
	}

	int n;

	cin >> n;

	for (int i = 0; i < n; ++i)
	{
	 	int a;
	 	cin >> a;
	 	for (int j = 0; j < a; ++j)
	 	{
	 		A[j][i] = true;
	 	}
	}

	int ans = 0;

	for (int i = 0; i < MAX_N; ++i)
	{
		for (int j = 0; j < MAX_N-1; ++j)
		{
			if (A[i][j] == true && A[i][j-1] == false)
			{
				ans++;
			}
		}
	}

	cout << ans << endl;
	return 0;
}