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)

using System;
using System.Collections.Generic;

namespace AizuOnLine_Lesson
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> data = Program.GetData();

            int minNum = 1000000000;
            int maxNum = 0;
            foreach (int num in data)
            {
                if (num < minNum)
                {
                    minNum = num;
                    maxNum = num;
                }

                if (maxNum < num)
                {
                    maxNum = num;
                }
            }

            int diff = maxNum - minNum;

            if(diff == 0)
            {
                Console.WriteLine(-1);
            }
            else
            {
                Console.WriteLine(diff);
            }
        }


        private static List<int> GetData()
        {


            List<int> data = new List<int>();

            int count = Convert.ToInt32(Console.ReadLine());

            for (int i = 0; i < count; i++)
            {
                data.Add(Convert.ToInt32(Console.ReadLine()));
            }

            return data;
        }
    }
}