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.Collections.Generic;
using System.Linq;

    public class PictureMatching
    {
        private static int[] Item;

        public static void Main(string[] args)
        {
            Input();
            Method();
            System.Console.ReadLine();
        }

        private static void Input()
        {
            var num = int.Parse(System.Console.ReadLine());
            Item = new int[num];
            for (int i = 0; i < num; i++)
            {
                Item[i] = int.Parse(System.Console.ReadLine());
            }
        }

        private static void Method()
        {
            var indItems = Item.Select((item, index) => new { index = index, Value = item });
            var minItem = indItems.Aggregate((min, item) => min.Value > item.Value ? item : min);

            if (minItem.index == Item.Length - 1)
            {
                int diffMin = 0;
                for (int i = 0; i < Item.Length - 1; i++)
                {
                    if (i == 0)
                    {
                        diffMin = (Item[i + 1] - Item[i]);
                    }
                    if ((Item[i + 1] - Item[i]) > diffMin)
                    {

                    }
                }

                System.Console.WriteLine(diffMin);
            }
            else
            {
                var maxItem = indItems.Aggregate((max, item) =>
                {
                    if (item.index < minItem.index) return minItem;
                    if (max.Value > item.Value) return max;
                    else return item;
                });

                System.Console.WriteLine(maxItem.Value - minItem.Value);
            }
        }

        private static int[] ToIntArray(string[] str)
        {
            IEnumerable<int> intArray = str.Select(x => int.Parse(x));
            return intArray.ToArray();
        }
    }