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 Ruby (2.3.3) (judge verdict: Accepted)

#set
n = gets.chomp.to_i
hight_arr = gets.chomp.split(" ").map(&:to_i)
count = 0
zeros = 0

#main
loop do
  break if hight_arr.count(0) == n
  zeros_arr = hight_arr
  zeros = 1
  (n - 1).downto(1) do |i|
    zeros_arr.delete_at(i) if zeros_arr[i] == zeros_arr[i - 1]
    
  end
  zeros_arr.delete_at(0) if zeros_arr[0] == 0
  zeros_arr.delete_at(-1) if zeros_arr[-1] == 0
  zeros += zeros_arr.count(0)

  

  count += zeros
  hight_arr = hight_arr.map{|j| j - 1 if j != 0 }
  0.upto(n - 1) do |k|
    hight_arr[k] = 0 if hight_arr[k].nil?
  end
end

print ("#{count}\n")