What is wrong in this code? Why this code for prime generator generates run time error while executingin SPOJ(coding website)?

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C#

programming

Peter wants to generate some prime numbers for his cryptosystem. Help him! Your task is to generate all prime numbers between two given numbers!


Input : The input begins with the number t of test cases in a single line (t<=10). In each of the next t lines there are two numbers m and n (1 <= m <= n <= 1000000000, n-m<=100000) separated by a space.

Output : For every test case print all prime numbers p such that m <= p <= n, one number per line, test cases separated by an empty line.

Example

Input:
2
1 10
3 5

Output:
2
3
5
7

3
5

My answer to the question is

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());
 
            for(int i= a;i<= b;i++)
            {
                int k = 0;
                {
                    for (int j = 1; j <= i; j++)
                    {
                        if (i % j == 0)
                        {
                            k++;
                        }
                    }
                    if (k == 2)
                    {
                        Console.WriteLine(i);
                    }
                }
            }
            Console.ReadLine();
            }
 
        }
    }

this renders perfectly the prime numbers of any range between the two specified numbers while running in VS2012.