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 Go (1.6) (judge verdict: Accepted)

// Package main provides
//
// File:  c.go
// Author: ymiyamoto
//
// Created on Tue Jan 22 16:31:27 2019
//
package main

import "fmt"

func scanSlice(slice []int) {
	for i := range slice {
		fmt.Scan(&slice[i])
	}
}

func main() {
	var N int
	fmt.Scan(&N)

	slice := make([]int, N)
	scanSlice(slice)

	ans := 0
	for i := 0; i < 100; i++ {
		num := 0
		above0 := false
		for j := range slice {
			if slice[j] > 0 {
				slice[j]--
				above0 = true
			} else {
				if above0 {
					num++
					above0 = false
				}
			}
		}

		if above0 {
			num++
		}
		ans += num
	}

	fmt.Println(ans)
}