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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws NumberFormatException, IOException {
		// TODO ?????????????????????????????????????????????
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		//??\?????¨
		int n = Integer.parseInt(br.readLine());

		int[] price = new int[n];
		for(int i = 0; i < n; i++){
			price[i] = Integer.parseInt(br.readLine());
		}

		int maxProfit = Integer.MIN_VALUE;
		int prevBuy = Integer.MAX_VALUE;

		for(int i = 0; i < n - 1; i++){
			int tmpHigh = 0;

			if(price[i] >= prevBuy){
				continue;
			}
			prevBuy = price[i];
			
			for(int j = i + 1; j < n; j++){
				if(price[j] > tmpHigh){
					tmpHigh = price[j];
				}
			}

			if(tmpHigh - price[i] > maxProfit){
				maxProfit = tmpHigh - price[i];
			}
		}


		System.out.println(maxProfit);

	}

}