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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <math.h>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
using namespace std;
typedef long long ll;
#define rep(i,s,n)for(ll i=s;i<n;i++)
#define repe(i,s,n)for(ll i=s;i<=n;i++)
#define rep_r(i,s,n)for(ll i=n;i>s;i--)
#define repe_r(i,s,n)for(ll i=n;i>=s;i--)
static const ll MOD = 1e9 + 7;
static const ll MAX_LL = (ll)1 << 62;

ll h[100] = {};
ll n;
bool allfalse() {
	rep(i, 0, n) {
		if (h[i] != 0) {
			return false;
		}
	}
	return true;
}

int main() {
	cin >> n;
	rep(i, 0, n)cin >> h[i];

	ll si = 0;
	ll ei = 0;
	ll minV = MAX_LL;
	ll ans = 0;
	while (1) {
		if (allfalse())break;

		if (h[ei] == 0 || ei == n - 1) {
			repe(j, si, ei) {
				h[j] -= minV;
			}
			ans++;
			if (ei == n - 1) {
				si = 0;
				ei = 0;
				continue;
			}
			else {
				ei++;
				si = ei;
				continue;
			}
		}
		else {
			minV = min(h[ei], minV);
		}
		ei++;
	}
	return 0;
}