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[] min = new int[2];
	
	void run() {
		// 入力
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int[] array = new int[200000];
		for(int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		int max = -1000000000;	
		searchMinimun(array, n-1);
		for(int i = n-1; i > 0; i--) {
			if(min[1] == i) searchMinimun(array, i-1);
			int tmp = array[i] - min[0];
			if(tmp > max) max = tmp;
		}
		System.out.println(max);
	}
	
	void searchMinimun(int[] array, int n) {
		min[0] = array[0];
		min[1] = 0;
		for(int i = 1; i <= n; i++) {
			if(min[0] > array[i]) {
				min[0] = array[i];
				min[1] = i;
			}
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
}