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()))
c=0
while max(h)>0:   
    ##断裂の数を数える
    if h[0] > 0:
      h.insert(0,0)
    if h[-1] > 0:
      h.append(0)
    p=0
    for i in range(len(h)-1):
      if h[i]>=1 and h[i+1]<=0:
        p+=1
    ##加算値は断裂
    c+=max(1,p)
    ##地盤沈下させる
    h = [n-1 for n in h]
    #print("c=",c,"p=",p,"h=",h)
    
print(c)