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: Wrong Answer)

from collections import deque
import numpy as np
N = int(input())
h = np.array(list(map(int,input().split())))
count = 0
tmp = deque()
tmp.append(h)
while True:
    st,en = -1,-1
    if len(tmp) == 0:
        break
    count += min(tmp[0])
    tmp[0] -= min(tmp[0])
    if list(tmp[0]) == [0]*len(tmp[0]):
        tmp.popleft()
        continue
    for i in range(len(tmp[0])):
        if st == -1 and tmp[0][i] != 0:
            st = i
        if st != -1 and tmp[0][i] == 0:
            en = i
        if st != -1 and tmp[0][i] == tmp[0][-1] and tmp[0][i] != 0:
            en = i+1
        if st != -1 and en != -1:
            tmp.append(tmp[0][st:en])
            st,en = -1,-1
    tmp.popleft()
print(count)