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)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Linq;

class Program
{
   static void Main(string[] args)
   {
        /* log(n^2) */
        //int n = int.Parse(Console.ReadLine());
        //int[] array = new int[n];
        //long maxv = -10000000000;

        //for(int i=0; i<n; i++)
        //{
        //    array[i] = int.Parse(Console.ReadLine());
        //}

        //for(int i=0; i < n; i++)
        //{
        //    for(int j=i+1; j < n; j++)
        //    {
        //        maxv = Math.Max(maxv, (array[j] - array[i]));
        //    }
        //}
        //Console.WriteLine(maxv);

        /* log(n) */
        int n = int.Parse(Console.ReadLine());
        long[] array = new long[n];
        long maxv = -1000000000000000000;

        for(int i=0; i<n; i++)
        {
            array[i] = long.Parse(Console.ReadLine());
        }

        long minv = array[0];

        for(int i=1; i<n; i++)
        {
            maxv = Math.Max(maxv, (array[i] - minv));
            minv = Math.Min(minv, array[i]);
        }

        Console.WriteLine(maxv);
   }
}