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(){
  int num,max,i,j,b;
  scanf("%d",&num);
  int a[num];
  for(i = 0 ;i<num ; i++){
    scanf("%d",&a[i]);
  }
  max = a[num-1] -a[0];
  for(i = num-1 ;i>0 ;i--){
    for(j = 0;j<=i-1 ;j++){
      if(a[i] ==a[j] && max <0) max =0; 
      else if((b=a[i]-a[j])>max)
       max=b;
    }
  }
  printf("%d\n",max);
  return 0;
}