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 Lua (Lua 5.3.5) (judge verdict: Accepted)

local read = io.read

local n = read("n")
local h_t = {}
for i = 1, n do
	h_t[i] = read("n")
end

local count = 0
for i = 1, n do
	local l, r = i, i
	local h_l = h_t[l]
	while h_t[r + 1] and h_t[r + 1] >= h_t[l] do
		r = r + 1
	end
	local r_plus_1 = h_t[r + 1] or 0

	for j = l, r do
		h_t[j] = h_t[j] - (h_l - r_plus_1)
	end
	count = count + h_l - r_plus_1
end

print(count)