Problem:
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Maximum Profit

You can obtain profits from foreign exchange margin transactions. For example, if you buy 1000 dollar at a rate of 100 yen per dollar, and sell them at a rate of 108 yen per dollar, you can obtain (108 - 100) × 1000 = 8000 yen.

Write a program which reads values of a currency $R_t$ at a certain time $t$ ($t = 0, 1, 2, ... n-1$), and reports the maximum value of $R_j - R_i$ where $j > i$ .

Input

The first line contains an integer $n$. In the following $n$ lines, $R_t$ ($t = 0, 1, 2, ... n-1$) are given in order.

Output

Print the maximum value in a line.

Constraints

$2 \leq n \leq 200,000$

$1 \leq R_t \leq 10^9$

Sample Input 1

6
5
3
1
3
4
3

Sample Output 1

3

Sample Input 2

3
4
3
2

Sample Output 2

-1

Solution in C++ (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
using namespace std;
static const int MAX = 200000;

int main()
{
	 int R[MAX], n;
	 
	 
	 cin >> n;
	 for( int i = 0; i<n; i++) cin >> R[i];
	 
	 int maxv = -2000000000; //设置一个足够小的初始值
	 int minv = R[0];
	 
	 for ( int i = 1; i <n; i++ ) {		//如果每次都在这一阶段直接读取R[i]，那么数组可以省去 
	 	maxv = max(maxv, R[i] - minv);   //更新最大值 
	 	minv = min(minv, R[i]);		    //暂存现阶段最小值 
	 } 
	 cout  << maxv << endl;
	 
	 return 0;
	 
}