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 <algorithm>
#include <functional>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <string>
#include <list>
#include <math.h>
#include <string.h>
#include <bitset>
using namespace std;

typedef pair<int, int> P;
#define INF (1LL<<60)
#define int long long
#define ll long long
#define mod 1000000007



signed main(){

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

	int ans = 0;
	while (true){
		int f = 0;
		while (h[f] == 0){
			f++;
			if (f == N) goto last;
		}
		int g = f;
		while (g<N && h[g]>0) g++;
		for (int i = f; i < g; i++) h[i]--;
		ans++;
	}
last:
	cout << ans << endl;


	return 0;
}