CF463B.Caisa and Pylons

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?

凯萨解决了糖果问题，现在正走在回家的路上。

凯萨在途中玩一款手机游戏。游戏中有 $n+1$ 个塔（pylon），编号从 $0$ 到 $n$。编号为 $0$ 的塔高度为 $0$，编号为 $i$（其中 $i > 0$）的塔高度为 $h_i$。游戏的目标是到达第 $n$ 个塔，玩家唯一允许的操作是从当前塔（设其编号为 $k$）跳到下一个塔（编号为 $k+1$）。每次执行该操作后，玩家的能量变化量为 $h_k - h_{k+1}$（若该值为负，则玩家损失能量）。玩家在任意时刻的能量值都必须为非负数。

初始时，凯萨站在编号为 $0$ 的塔上，且能量为 $0$。游戏提供一项特殊功能：玩家可花费 1 美元，将任意一个塔的高度增加 $1$。凯萨可以多次使用该功能，但他不想花太多钱。请问：他至少需要花费多少美元才能达成游戏目标？

The first line contains integer n (1 ≤ n ≤ 105). The next line contains n integers _h_1, _h_2, ..., h__n (1  ≤  h__i  ≤  105) representing the heights of the pylons.

第一行包含一个整数 $n$（$1 \leq n \leq 10^5$）。第二行包含 $n$ 个整数 $h_1, h_2, \dots, h_n$（$1 \leq h_i \leq 10^5$），表示各个塔架的高度。

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

输出一个数字，表示Caisa支付的最少美元数。

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.

在第一个样例中，他可以支付 4 美元，将编号为 0 的支柱高度增加 4 个单位。然后他便可以安全地到达最后一个支柱。