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 C (judge verdict: Accepted)

#include<stdio.h>
int main()
{
  int i,n,x,before,after,min;
  scanf("%d",&n);
  scanf("%d%d",&before,&after);
  if(before<after) min=before;
  else min=after;
  for(i=2;i<n;i++)
    {
      scanf("%d",&x);
      if(x>after) after=x;
      if(x-min>after-before)
	{
	  after=x;
	  before=min;
	}
      if(x<min) min=x;
    }
  printf("%d\n",after-before);
  return 0;
}