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;
typedef long long ll;
typedef long double ld;
using Graph = vector<vector<ll>>;
using P = pair<int,int>;

#define MOD 1000000007
#define INF 1000000
#define PI 3.14159265358979323846264338327950L
#define MAX_N 200010
#define lb lower_bound //[2,4)=lb(4)-lb(2);

#define REP(i,n) for(int i=0;i<n;++i)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl

/*
0,0,0,0というやつを
水やりして
1,2,2,1にする
*/

bool isnull(vector<int> h)
{
  int n=h.size();
  for (int i=0;i<n;i++)
  { 
    if (h[i]!=0) return (false);
  }
  return (true);
}
 
int main()
{
  int N;cin>>N;
  vector<int> h(N);
  for (int i=0;i<N;i++)
    cin>>h[i];
  
  int i=0;
  int count=0;
  while (!isnull(h))
  {
    i=0;
    while (h[i]==0)
    {
      i++; 
    }
    while (h[i]>=1)
    {
      h[i]-=1;
      i++;
    }
    count++;
  }
  cout<<count<<endl;
}