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 PyPy3 (2.4.0) (judge verdict: Accepted)

#116C
n = int(input())
h = list(map(int,input().split()))
s = set([])

for i in range(n):
    s.add(h[i])
s = list(s)
s.append(0)
s.sort()

m = len(s)
    
flag = [0] * (n+1)
flag[0] = 1
ans = 0

for i in range(m-1):
    a = 0
    b = s[i+1]-s[i]
    
    for j in range(n):
        if flag[j+1] == 0 and flag[j] == 1:
            a += 1
    
    for j in range(n):
        if h[j] == s[i+1]:
            flag[j+1] = 1
    ans += (a * b)
    
print(ans)