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 (3.8.2) (judge verdict: Wrong Answer)

def down(H, n):
  x = min(H)
  n += x
  for i in range(len(H)):
    H[i] -= x
  return H, n

N = int(input())
H = list(map(int, input().split()))
n = 0
H, n = down(H, n)
print(H)

while not all(h == 0 for h in H):
  L = []
  H0 =[]
  for h in H:
    if h != 0:
      L.append(h)
    else:
      if L:
        L, n = down(L, n)
      H0 += L
      H0.append(0)
      L = []
  if L:
    L, n = down(L, n)
    H0 += L
  H = H0
  print(H)

print(n)