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 i,j;
  int n,r[200000];
  int MAX;
  int max[2],min[2];
  scanf("%d",&n);
  for(i=0;i<n;i++) scanf("%d",&r[i]);
  max[0]=1;
  max[1]=r[1];
  min[0]=0;
  min[1]=r[0];
  for(i=0;i<n;i++){
    if(max[1]<r[i]){
      max[0]=i;
      max[1]=r[i];
    }
    if(min[1]>r[i]){
      min[0]=i;
      min[1]=r[i];
    }
  }
  if(max[0]>min[0]) MAX=max[1]-min[1];
  else{
    MAX=r[1]-r[0];
    for(i=0;i<n-1;i++){
      for(j=i+1;j<n;j++){
	if(MAX<r[j]-r[i]){
	  MAX=r[j]-r[i];
	}
      }
    }
  }
  printf("%d\n",MAX);
  return(0);
}