Caisa and Pylons

题意翻译

Caisa 在玩游戏。 游戏中有从 $0$ 到 $n$ 编号的 $(n+1)$ 个电塔，编号为 $0$ 的电塔高度为 $0$，编号为 $i$ 的电塔高度为$h_i$。 游戏的目标是到达第 $n$ 个电塔，而玩家唯一能做的就是从当前电塔（不妨设编号为 $k$）跳到下一个电塔（编号为 $k+1$）。当玩家这样做时，他的能量值会增加 $h_k-h_{k+1}$（如果该值为负数，则玩家失去能量值）。 玩家必须保证在任何时候他的能量值非负。 Caisa 从 $0$ 号塔开始，问他在一开始最少需要多少能量值才能达到游戏的目标？ ### 输入格式 第一行一个正整数 $n(1 \le n \le 10^5)$。 第二行 $n$ 个正整数 $h_1,h_2,...,h_n(1 \le h_i \le 10^5)$。 ### 输出格式 一行，一个整数，表示 Caisa 在游戏开始时最少需要多少能量值才能达到游戏的目标。

题目描述

Caisa solved the problem with the sugar and now he is on the way back to home. Caisa is playing a mobile game during his path. There are $ (n+1) $ pylons numbered from $ 0 $ to $ n $ in this game. The pylon with number $ 0 $ has zero height, the pylon with number $ i $ $ (i>0) $ has height $ h_{i} $ . The goal of the game is to reach $ n $ -th pylon, and the only move the player can do is to jump from the current pylon (let's denote its number as $ k $ ) to the next one (its number will be $ k+1 $ ). When the player have made such a move, its energy increases by $ h_{k}-h_{k+1} $ (if this value is negative the player loses energy). The player must have non-negative amount of energy at any moment of the time. Initially Caisa stand at $ 0 $ pylon and has $ 0 $ energy. The game provides a special opportunity: one can pay a single dollar and increase the height of anyone pylon by one. Caisa may use that opportunity several times, but he doesn't want to spend too much money. What is the minimal amount of money he must paid to reach the goal of the game?

输入输出格式

输入格式

The first line contains integer $ n $ $ (1<=n<=10^{5}) $ . The next line contains $ n $ integers $ h_{1} $ , $ h_{2} $ , ..., $ h_{n} $ $ (1<=h_{i}<=10^{5}) $ representing the heights of the pylons.

输出格式

Print a single number representing the minimum number of dollars paid by Caisa.

输入输出样例

输入样例 #1

5
3 4 3 2 4

输出样例 #1

4

输入样例 #2

3
4 4 4

输出样例 #2

4

说明

In the first sample he can pay $ 4 $ dollars and increase the height of pylon with number $ 0 $ by $ 4 $ units. Then he can safely pass to the last pylon.