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: Time Limit Exceeded)

#include<iostream>
#include<string>
#include<algorithm>
#include<list>
#include<cmath>
#include<vector>
#include<cstdio>
using namespace std;
int main(void){
	int n,i,mini,ans=0;
	cin>>n;
	int gar[n];
	for(i=0;i<n;i++)cin>>gar[i];
	while(1){
		mini=101;
		int left=0,right=0,center=0;
		i=0;
		while(i<n){
			if(gar[i]<mini&&gar[i]> 0){
				center=i;
				mini=gar[i];
			}
			i++;
		}
//		cout<<"mini="<<mini<<endl;
		while(center-left>0){
			if(gar[center-left-1]>0)left++;
			else break;
		}
		while(center+right+1<n){
			if(gar[center+right+1]>0)right++;
			else break;
		}
//		cout<<"left="<<left<<endl;
//		cout<<"right="<<right<<endl;
		for(i=center-left;i<=center+right;i++)gar[i]--;
		ans++;
		int sum=0;
		for(i=0;i<n;i++)sum+=gar[i];
		if(sum==0) break;
//		for(i=0;i<n;i++)cout<<gar[i]<<" ";
//		cout<<endl;
	}
	cout<<ans<<endl;
	return 0;
}