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: Runtime Error)

N = int(input())
listh = list(map(int, input().split()))
listans = [listh[0]]
for n in range(1,N-1):
    if (listh[n+1]-listh[n])*(listh[n]-listh[n-1])<=0:
        listans.append(listh[n])
listans.append(listh[N-1])        
#print(listans)
l =len(listans)
listans2 = []
for n in range(l-1):
    if listans[n] == listans[n+1]:
        pass
    else:
        listans2.append(listans[n])
listans2.append(listans[l-1])        
#print(listans2)    
L = len(listans2)
#print(L)
listodd = [listans2[x] for x in range(L) if x%2 ==1]
#print(listodd)
listeven = [listans2[x] for x in range(L) if x%2 ==0]
#print(listeven)
if L%2 == 0:
    if listeven[0]>listodd[0]:
        del listodd[-1]
        ans = sum(listeven)-sum(listodd)
        print(ans)

    else:  
        del listeven[0]
        ans = sum(listodd)-sum(listeven)  
        print(ans)

else:     
    if listeven[0]>listodd[0]:
        ans = sum(listeven)-sum(listodd)
        print(ans)

    else:
        del listeven[-1]
        if len(listeven)>0
        del listeven[0]
        ans = sum(listodd)-sum(listeven)
        print(ans)