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 JAVA (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
	
	int[] currency;
	int[] minCurrency;
	int maxProfit;

	public static void main(String[] args) {
		Main main = new Main();
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		main.currency = new int[n];
		main.minCurrency = new int[n];
		for (int i = 0; i < n; i++) {
			main.currency[i] = in.nextInt();
		}
		main.maxProfit = main.currency[1] - main.currency[0];
		if (main.currency[0] < main.currency[1]) {
			main.minCurrency[0] = main.currency[0];
		} else {
			main.minCurrency[0] = main.currency[1];
		}
		for (int i = 2; i < n; i++) {
			main.setMins(i);
		}
		System.out.println(main.maxProfit);
	}
	
	public void setMins(int index) {
		int min = this.minCurrency[index - 2];
		this.maxProfit = (currency[index] - min > maxProfit)? currency[index] - min : maxProfit;
		this.minCurrency[index - 1] = (this.currency[index] < min)? this.currency[index] : min;
	}

	public void printList(int[] list) {
		for (int i = 0; i < list.length; i++) {
			System.out.print(list[i] + " ");
		}
		System.out.println();
	}
	
}