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 PyPy2 (7.3.0) (judge verdict: Wrong Answer)

"""
8
4 23 75 0 23 96 50 100
"""

[0,75,0,96,50,100]


n = int(raw_input())
ais = map(int, raw_input().split(' ')) #set()


r = [0]
for i in range(len(ais)):
	if (ais[i-1] if i-1 >= 0 else 0) <= ais[i] > (ais[i+1] if i+1 < len(ais) else 0): r.append(ais[i])
	if (ais[i-1] if i-1 >= 0 else 0) >= ais[i] < (ais[i+1] if i+1 < len(ais) else 0): 
		if i:
			r.append(ais[i])

	
t = 0
for i in range(0,len(r),2):
	if i + 1 < len(r):
		u,v = r[i],r[i+1]
		t += v-u
print t if len(ais) > 1 else ais[0]