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: Accepted)


N = int(input())

l = [int(x) for x in input().split(" ")]



mat = []
for _ in range(N):
	mat.append([])

for index, i in enumerate(l):
	for _ in range(i):
		mat[index].append(1)
	while len(mat[index]) != max(l):
		mat[index].append(0)


def trans(A:list) -> list:
    ans = []
    for col in range(len(A[0])):
        l = []
        for line in range(len(A)):
            l.append(A[line][col])
        ans.append(l)

    return ans    

garden = trans(mat)


count = 0
for line in reversed(garden):
	mark = False
	for index, i in enumerate(line):
		if i == 1 and mark == False:
			count += 1
			line[index] = 0
			mark = True
		
		elif i == 1 and mark == True:
			line[index] = 0

		elif i == 0:
			mark = False


print(count)