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: Accepted)

#include <bits/stdc++.h>
#define sz(x) (int)(x).size()
#define For(i, a, b) for (int i = int(a); i < int(b); i++)
#define Dor(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define Foz(i, a) For(i, 0, a)
#define Doz(i, a) Dor(i, 0, a)
#define Trav(e, v) for (auto& e : v)
#define pb push_back
#define mp make_pair
#define all(x) begin(x), end(x)
using namespace std;
using ll = long long;
using ii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vii = vector<ii>;
template <typename T> bool ckmin (T& a, T b) { return (b < a) ? a = b, 1 : 0; }
template <typename T> bool ckmax (T& a, T b) { return (b > a) ? a = b, 1 : 0; }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#ifdef XVENOM
	#define errp(...) fprintf(stderr, __VA_ARGS__)
	#define dbg(...) errp("[%s]: ", #__VA_ARGS__), dbg_str(__VA_ARGS__)
#else
	#define errp(...)
	#define dbg(...)
#endif
template <typename U, typename V> string to_string (pair<U, V>);
string to_string (string& e) { return "\"" + e + "\""; }
string to_string (char e) { return "\'" + string(1, e) + "\'"; }
string to_string (bool e) { return e ? "true" : "false"; }
template <typename T> string to_string (T e) {
	string s = "[ ";
	for (auto& x : e) s += to_string(x) + " ";
	return s + "]";
}
template <typename U, typename V> string to_string (pair<U, V> e) {
	return "(" + to_string(e.first) + ", " + to_string(e.second) + ")";
}
void dbg_str () { errp(" \n"); }
template <typename U, typename... V> void dbg_str (U u, V... v) {
 	errp(" %s", to_string(u).c_str()); dbg_str(v...);
}
/* --- */
int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	/* --- */
	int n;
	cin >> n;
	vi a(n), f(n);
	Foz(i, n) cin >> a[i];
	f[0] = a[0];
	For(i, 1, n) f[i] = f[i - 1] + max(0, a[i] - a[i - 1]);
	cout << f[n - 1] << '\n';
}