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>
//#include <boost/multiprecision/cpp_int.hpp>
#define rep(i,m,n) for(int i=m;i<n;i++)
#define co(n) cout<<n<<endl
#define all(n) (n).begin(),(n).end()
#define pb(n,m) n.push_back(m)
#define pi(n,m) n.insert(n.begin(),m);
#define ee(n) n.erase(n.end()-1)
#define eb(n) n.erase(n.begin())
using namespace std;
//using bint=boost::multiprecision::cpp_int;
typedef long long ll;
typedef unsigned long long ull;

int main(){
  int n,m=0,ans=0; cin>>n;
  vector<int> a(n+1);
  rep(i,0,n){
    cin>>a[i];
    m=max(m,a[i]);
  }
  a[n]=-1;
  rep(i,1,m+1){
    int c=0;
    bool f=false;
    rep(j,0,n+1){
      if(a[j]>=i) f=true;
      else if(f){
        ans++;
        f=false;
      }
    }
    ans+=c;
  }
  co(ans);
  return 0;
}