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 {

	  //given n times, and R, an array of currencies/rates
	public int compute_maxprofit(int n,int[] R) {
		int max_profit = -999999999;
		int min_price = R[0];
		for(int i = 0; i < n -1; i ++) {
			if(R[i] < min_price) {
				min_price = R[i];
			}
			max_profit = Math.max(max_profit, R[i+1] - min_price);
		}
		return max_profit;
	}
	
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int rSize = in.nextInt();
		int[] R = new int[rSize];
		
		for(int i = 0; i < rSize; i++) {
			R[i] = in.nextInt();
		}
		
		Main test = new Main();
		System.out.println(test.compute_maxprofit(rSize, R));
	}
}