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: Accepted)

n = int(input())
h = list(map(int,input().split()))
tmp = [0 for i in range(n)]
ans = 0
right = 0
left = n-1

while tmp != h:
    for i in range(n):
        if tmp[i] != h[i]:
            right = i
            left = i
            break
    for i in range(i+1,n):
        if tmp[i] == h[i]:
            left = i-1
            break
        elif i == n-1 and tmp[n-1] != h[n-1]:
            left = n-1
            break
    for i in range(right,left+1):
        tmp[i] += 1
    ans += 1
#    print(right,left,ans)
#    print(tmp)

print(ans)