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>
#define min(p,q)((p)<(q)?(p):(q))

int a[110];
int f(int l,int r,int k){
	if(l==r)return 0;
	int m=1e9;
	for(int i=l;i<r;i++)m=min(m,a[i]);
	int ans=m-k;
	int pre=l-1;
	for(int i=l;i<r;i++)if(a[i]==m){
		ans+=f(pre+1,i,m);
		pre=i;
	}
	ans+=f(pre+1,r,m);
	return ans;
}

int main(){
	int n;
	scanf("%d",&n);
	for(int i=0;i<n;i++)scanf("%d",a+i);
	printf("%d",f(0,n,0));
}