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: Wrong Answer)

public static class Program
{
  public static void Main(string[] args)
  {
    int num = int.Parse(System.Console.ReadLine());
    
    ulong[] input = new ulong[num];
    for(int i = 0; i < num; i++)
    {
      string str = System.Console.ReadLine();
      input[i] = ulong.Parse(str);
    }
    
    ulong max = 0;
    ulong min = ulong.MaxValue;
    int minPoint = 0;
    int maxPoint = 0;
    ulong maxDiff = 0;
    ulong diff = 0;
    for(int i = 0; i < num; i++)
    {
      if(min > input[i])
      {
        min = input[i];
        minPoint = i;
      }
      
      if(max < input[i])
      {
        max = input[i];
        maxPoint = i;
      }
      
      if(minPoint < maxPoint)
      {
        diff = max - min;
      }
      
      if(diff > maxDiff)
      {
        maxDiff = diff;
      }
    }
    
    System.Console.WriteLine(maxDiff);
  }
}