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>
#include<stdlib.h>
#include<math.h>

int main(){

  int num,i,*r,maxv,minv;
 
  while(1){

    scanf("%d",&num);
    if(num>=2&&num<=2000000) break;
  }
    r = (int *)malloc(num * sizeof(int));
    for(i=0;i<num;i++){
      scanf("%d",&r[i]);
      if(r[i]<1||r[i]>pow(10,9)) break;
      }
    maxv = r[1]-r[0];
    minv = r[0];
    for(i=1;i<=num-1;i++){
      if(r[i]-minv>maxv)
	maxv = r[i]-minv;
      else
	maxv = maxv;
      
      if(r[i]<minv)
	minv = r[i];
      else
	minv = minv;
    }
    printf("%d\n",maxv);



  return 0;
}