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.InputStreamReader;
import java.lang.Math;

/*Question
/FX????????§????????°?????????????????¨????????????????????¨??§????????????????????????????????¨?????§????????????
/????????°????????????100???????????? 1000???????????????????????????????????? 1?????? 108???????????£??????????£??????¨???(108??? ??? 100???) ?? 1000?????? =
8000??????????????????????????¨?????§????????????
/???????????¨????????????????????? t?????????????????? Rt (t=0,1,2,,,n???1)?????\?????¨??????????????????????????§??????????????? Rj???Ri (????????????j>i??¨??????) ????????§???????±??????????????????????
*/

/*Input
/?????????????????´??° n?????????????????????????¶???? n ????????´??° Rt (t=0,1,2,,,n???1) ????????????????????????????????? 
*/

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader sc = new BufferedReader(new InputStreamReader(System.in));
		//????????¨
		long k;
		/*??\???
		/??????????´???°?????\???????¬??????°????????\???
		*/
		int n = Integer.parseInt(sc.readLine());
		long[] r = new long[n];
		for(int i = 0;i < n;i++){
			r[i] = Long.parseLong(sc.readLine());
		}
		/*??°??????fxariganetokasu???????????????
		/??????????????£??????????????§??????
		*/
		k = fxariganetokasu(r);
		System.out.println(k);
	}

	/*fxariganetokasu????????????
	/????????????????????????????????§????±???????
	/@return long
	*/

	public static long fxariganetokasu(long[] r) {
		//????????¨?????¨??????????????\???????????????????????????????????\????????????????????????int???????°??????§??????????????????????????????
		long s = r[1] - r[0];
		//????°??????\????????¨????????????????????\????????????
		long minn = r[0];
		for (int i = 1;i < r.length;i++) {
			s = Math.max(s,r[i] - minn);
			minn = Math.min(minn,r[i]);
		}
		return s;
	}
}