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 Fortran (gfortran v4.8.4) (judge verdict: Runtime Error)

program garden
  implicit none

  integer :: n, min, max, i, cnt, j, k, t, s
  integer, allocatable :: h(:), h2(:)

  read(*,*) n
  allocate(h(n))
  allocate(h2(n))
  read(*,*) h

  min = minval(h)
  max = maxval(h)


  if (product(h) /= 0) then
     cnt = 1
  else
     cnt = 0
  end if

  
  do j = min, max
     do t = 1, n
        if(h(t) >= j) then
           h2(t) = h(t) - j 
        else
           h2(t) = 0
        end if

        
     end do
     
     do i = 1, n
        if (h2(i) >= 1) then
           if(product(h2(i:n)) == 0) then
              do k = i, n
                 if(h2(k) == 0) then
                    cnt = cnt + 1
                    exit
                 end if
              end do
              do s = i, k
                 h2(s) = 0
              end do
              
           else
              cnt = cnt + 1
              exit
           end if
        end if
     end do
     
  end do

  write(*,*) cnt
end program garden