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>

int main(void)

{

 int n, i, j;
 int a[200000];
 int k = 0;
 int max = 0;

 scanf("%d", &n);

 for(i = 0;i < n; i++)
{

 scanf("%d", &a[i]);

 }

 for(i = 0;i < n; i++)
{
  for(j = i+1; j < n; j++)
{
  if(a[j] - a[i] > max || k == 0)
 {
  max = a[j] - a[i];
  k = 1;
 } 
}
}
 printf("%d\n", max);

 return 0;
}