System.IndexOutOfRangeException

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
</configuration>

AssemblyInfo.cs

using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

// General Information about an assembly is controlled through the following 
// set of attributes. Change these attribute values to modify the information
// associated with an assembly.
[assembly: AssemblyTitle("Store Credit - Small (C-Sharp)")]
[assembly: AssemblyDescription("")]
[assembly: AssemblyConfiguration("")]
[assembly: AssemblyCompany("")]
[assembly: AssemblyProduct("Store Credit - Small (C-Sharp)")]
[assembly: AssemblyCopyright("Copyright ©  2014")]
[assembly: AssemblyTrademark("")]
[assembly: AssemblyCulture("")]

// Setting ComVisible to false makes the types in this assembly not visible 
// to COM components.  If you need to access a type in this assembly from 
// COM, set the ComVisible attribute to true on that type.
[assembly: ComVisible(false)]

// The following GUID is for the ID of the typelib if this project is exposed to COM
[assembly: Guid("790613f6-6e64-4ab3-ad7f-38f4536f05c8")]

// Version information for an assembly consists of the following four values:
//
//      Major Version
//      Minor Version 
//      Build Number
//      Revision
//
// You can specify all the values or you can default the Build and Revision Numbers 
// by using the '*' as shown below:
// [assembly: AssemblyVersion("1.0.*")]
[assembly: AssemblyVersion("1.0.0.0")]
[assembly: AssemblyFileVersion("1.0.0.0")]

Program.cs

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

namespace scred {
    class Program
    {
        static int n;
        static void Main(string[] args)
        {
            String nS = Console.ReadLine();
            n = Convert.ToInt32(nS);
            for (int ni = 1; ni <= n; ni++)
            {
                String cS = Console.ReadLine();
                int c = Convert.ToInt32(cS);
                String iS = Console.ReadLine();
                int i = Convert.ToInt32(iS);
                String[] p = Console.ReadLine().Split(' ');
                for (int a = 1; a <= p.Length-2; a++)
                {
                    bool done = false;
                    for (int b = 1; b <= p.Length-2; a++)
                    {
                        if ((Convert.ToInt32(p[a]) + Convert.ToInt32(p[b])) == c)
                        {
                            Console.WriteLine("Case #" + ni + ": " + a + " " + b);
                            Thread.Sleep(1000);
                            done = true;
                            break;
                        }
                        else
                        {
                            done = false;
                        }
                    }
                    if (done) break;
                }
            }
        }
    }
}