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: Time Limit Exceeded)

#include<stdio.h>
#include<stdlib.h>
#define MAX 200000

int main(){
  int n,i,j;
  int R[MAX];
  int maxnum;

  scanf("%d",&n);
  if( n < 2 || MAX < n ) exit(2);

  for( i = 0 ; i < n ; i++ ){
    scanf("%d",&R[i]);
    if( R[i] < 1 || 1000000000 < R[i] )
      exit(3);
  }

  maxnum = R[n-1] - R[n-2]; 
  for( i = n-1 ; i >= 0 ; i-- )
    {
      for( j = i-1 ; j >= 0 ; j--)
	{
	  if( i == j ) break;
	  if( maxnum < R[i] - R[j] )
	    maxnum = R[i] - R[j];
	}
    }

  printf("%d\n",maxnum);
 
  return 0;
}