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: Runtime Error)

package main
import . "fmt"
func main() {
  var n int
  var h []int
  Scan(&n)
  h = make([]int,n)
  for i:=0;i<n;i++ { Scanf("%d",&h[i]) }
  Println(watering(h))
}
func watering(h []int) int {
  var n int = len(h)
  if n == 0 { return 0 }
  if n == 1 { return h[0] }
  if max(h) == 0 { return 0 }
  var m int = min(h)
  for i:=0;i<n;i++ { h[i] -= m }
  var k int = 0
  for i:=0;i<n;i++ {
    if h[i] != 0 {
      k = i
      break
    }
  }
  for i:=1;i<n;i++ {
    if h[i] == 0 {
      m += watering(h[k:i])
      i++
      k = i
    }
  }
  m += watering(h[k:n])
  return m
}
func min(a []int) int {
  var m int = a[0]
  for i:=1;i<len(a);i++ {
    if m > a[i] { m = a[i] }
  }
  return m
}
func max(a []int) int {
  var m int = a[0]
  for i:=1;i<len(a);i++ {
    if m < a[i] { m = a[i] }
  }
  return m
}