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: Wrong Answer)

N = int(input())
array = input().split(' ')
harray = []
for z in array:
    z = int(z)
    harray.append(z)
counter = 0
while harray != [0]*N:
    if 0 not in harray:
        a = min(harray)
        for i in range(len(harray)):
            harray[i] -= a
        counter += a
    else:
        zeroarray = [j for j, x in enumerate(harray) if x == 0]
        if len(zeroarray) == 1:
            if zeroarray[0] == 0:
                a = min(harray[1:])
                for y in range(1,N):
                    harray[y] -= a
                counter += a
            elif zeroarray[0] == N-1:
                a = min(harray[:N-2])
                for y in range(N-1):
                    harray[y] -= a
                counter += a
            else:
                a = min(harray[:zeroarray[0]])
                for y in range(zeroarray[0]):
                    harray[y] -= a
                counter += a
                a = min(harray[zeroarray[0]+1:])
                for y in range(zeroarray[0]+1,N):
                    harray[y] -= a
                counter += a
        else:
            for k in range(len(zeroarray)-1):
                if zeroarray[0] != 0:
                    a = min(harray[:zeroarray[0]])
                    for y in range(zeroarray[0]):
                        harray[y] -= a
                    counter += a
                if zeroarray[k+1] - zeroarray[k] == 1:
                    continue
                else:
                    a = min(harray[zeroarray[k]+1:zeroarray[k+1]])
                    for y in range(zeroarray[k]+1,zeroarray[k+1]):
                        harray[y] -= a
                    counter += a
                if zeroarray[-1] != N-1:
                    a = min(harray[zeroarray[-1]+1:])
                    for y in range(zeroarray[-1]+1,N):
                        harray[y] -= a
                    counter += a
        

print(counter)