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.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication30
{
    class Program
    {
        static void Main()
        {
            List<int> R = new List<int>();
            int A = int.Parse(Console.ReadLine()), S = int.MinValue;int U = int.MinValue;
            for (int B = 0; B < A; B++)
            {
                int L = int.Parse(Console.ReadLine());
                R.Add(L);
            }
            for (int C = R.Count - 1; C > -1; C--)
            {
                    if (S >= R[C]||U>=R[C]) continue;
                    for (int D = C - 1; D > -1; D--)
                    {
                        if (R[C] - R[D] > S) { S = R[C] - R[D]; if (R[D] == 0) { break; } U = R[C]; }
                    }
            }
            Console.WriteLine(S);
            }
        }
    }