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,ans=0;
    scanf("%d",&n);
    int h[n];
    for (int i=0; i<n; i++){
        scanf("%d",&h[i]);
    }
    while(1){
        int flag=0;
        for (int i=0; i<n; i++){
            if (flag==0){
                if (h[i]!=0){
                    flag=1;
                    h[i]--;
                }
            } else if (flag==1){
                if (h[i]!=0){
                    h[i]--;
                } else {
                    flag=2;
                }
            }
        }
        if (flag==0){
            break;
        } else {
            ans++;
        }
    }
    printf("%d\n",ans);
    return 0;    
}