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 Python (3.4.3) (judge verdict: Accepted)

n=int(input())
h=list(map(int,input().split()))

def remove_dpl(x):
  it=iter(x)
  before=next(it)
  res=[before]
  for e in it:
    if e!=before:
      res.append(e)
      before=e
  return res

c=0
h=remove_dpl(h)
while len(h)!=1:
  if h[0]>h[1]:
    c+=h[0]-h[1]
    h[0]=h[1]
  if h[len(h)-2]<h[len(h)-1]:
    c+=(h[len(h)-1]-h[len(h)-2])
    h[len(h)-1]=h[len(h)-2]
  for i in range(1,len(h)-1):
    if h[i]>h[i-1] and h[i]>h[i+1]:
      c+=h[i]-max(h[i-1],h[i+1])
      h[i]=max(h[i-1],h[i+1])
  h=remove_dpl(h)
print(c+h[0])