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: Wrong Answer)

n = gets.chomp.to_i
h = gets.chomp.split
for i in 0..n
  h[i] = h[i].to_i
end
cnt = 0
id = 0

while true
  if h[id] != 0
    h[id] -= 1
  else
    tmp = id
    while id < n - 1
      if h[id + 1] == 0
        id += 1
      else
        break
      end
    end
    if tmp != 0
      cnt += 1
    end
  end
  
  if id == n - 1
    cnt += 1
    id = 0
  else
    id += 1
  end
  
  if0 = 0
  for i in 0..(n - 1)
    if h[i] != 0
      if0 += 1
      break
    end
  end
  if if0 == 0
    puts cnt
    break
  end
end