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: Runtime Error)

n=int(input())
h=list(map(int,input().split()))
if n==1:
    print(h[0])
elif n==2:
    print(max(h))
else:
    h.append(0)
    h.insert(0,0)
    
    ans=0
    f=[0 for i in range(n+2)]
    
    for i in range(10010):
        a=1
        x=[]
        for j in range(n+2):
            if h[j]<=f[j]:
                x.append(j)
        m=len(x)
        if m==n+2:
            break
        a=m-1
        for j in range(m-1):
            if x[j]+1==x[j+1]:
                a-=1
        ans+=a
        for j in range(n+2):
            f[j]+=1
        
print(ans)