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.io.IOException;

class Main{

  public static void main(String[] args)throws IOException{
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    int N = Integer.parseInt(br.readLine());
    int[] a = new int[N];

    for(int i = 0; i < N; i++){
      a[i] = Integer.parseInt(br.readLine());
    }

    int min = a[0];
    int max = a[1]-a[0];

    for(int i = 0; i < N-1; i++){
      if(i == N - 1){
        min = minv(min, a[i-1]);
        max = maxv(max, a[i] - min);
      }else{
        min =  minv(min, a[i]);
        max = maxv(max, a[i+1] - min);
      }
    }


    System.out.println(max);
  }

  public static int minv(int min, int a){
    if(min >= a){
      return a;
    }else{
      return min;
    }
  }

  public static int maxv(int max, int a){
    if(max <= a)return a;
    else return max;
  }

}