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: Accepted)

program main
   implicit none
   integer n
   integer,allocatable,dimension(:):: h
   integer:: i,j,counter=0
   read(*,*)n
   allocate(h(n))
   read(*,*)h
   do i=1,n
10       continue
      do j=n,i,-1

         if(all(h(i:j)>0))then
            h(i:j)=h(i:j)-1
            counter=counter+1
            goto 10
         endif
      enddo
   enddo
   write(*,*)counter
end program main