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.

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.

Constraints

• $1 \leq N \leq 100$
• $0 \leq h_i \leq 100$
• All values in input are integers.

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

见题面 Input 部分

见题面 Output 部分