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 C (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>

int main(void){
    int N,h[100];
    int i,j,num,l,r;
    scanf("%d",&N);
    for(i=0;i<N;i++){
        scanf("%d",&h[i]);
    }
    l=0;    num=0;  h[i]=-1;    j=0;
    while(1){
        if(h[l]==0){
            l++;
            r=l;
        }else if(h[r]>0){
            r++;
            continue;
        }else if(h[r]<=0){
            for(i=l;i<r;i++){
                h[i]--;
            }
            l=0;    r=0;
            num++;
            continue;
        }
        if(h[l]==-1)  break;

    }
    printf("%d\n",num);
    return 0;
}