Problem:
Score: 300 points

Problem Statement

Find the minimum prime number greater than or equal to X.

Notes

A prime number is an integer greater than 1 that cannot be evenly divided by any positive integer except 1 and itself.

For example, 2, 3, and 5 are prime numbers, while 4 and 6 are not.

Constraints

2 \le X \le 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X

Output

Print the minimum prime number greater than or equal to X.

Sample Input 1

20

Sample Output 1

23

The minimum prime number greater than or equal to 20 is 23.

Sample Input 2

2

Sample Output 2

2

X itself can be a prime number.

Sample Input 3

99992

Sample Output 3

100003

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

namespace PaizaTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var x = int.Parse(Console.ReadLine());

            // 素数を求める
            var max = 110000;

            var list = new List<int>();
            for (int i = 2; i < max; i++)
            {
                if (list.Any(s => i % s == 0))
                {
                    continue;
                }

                list.Add(i);
            }
            var value = list.First(i => i >= x);
            Console.WriteLine(value);
        }
        //static void Main(string[] args)
        //{

        //var nk = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
        //// 2 <= n <= 10^5
        //// 1 <= k <= n - 1

        //// グーの勝利点: r
        //// チョキの勝利点: s
        //// パーの勝利点: p
        //var rsp = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
        //var t = Console.ReadLine();
        //var score = 0;
        //var rScore = rsp[0];
        //var sScore = rsp[1];
        //var pScore = rsp[2];
        //var myHandHistory = new List<int>();
        //// r = 1;
        //// s = 2;
        //// p = 3;

        //for (int i = 0; i < nk[0]; i++)
        //{
        //    var enemyHand = t[i];
        //    switch (enemyHand)
        //    {
        //        case 'r':
        //            myHandHistory.Add(3);
        //            if (myHandHistory.Count - 1 > nk[1] && myHandHistory[i - nk[1]] != 3)
        //            {
        //                score += pScore;
        //            }
        //            break;
        //        case 's':
        //            myHandHistory.Add(1);
        //            if (myHandHistory.Count - 1 > nk[1] && myHandHistory[i - nk[1]] != 1)
        //            {
        //                score += rScore;
        //            }
        //            break;
        //        case 'p':
        //            myHandHistory.Add(2);
        //            if (myHandHistory.Count - 1 > nk[1] && myHandHistory[i - nk[1]] != 2)
        //            {
        //                score += sScore;
        //            }
        //            break;
        //        default:
        //            break;
        //    }
        //}
        //Console.WriteLine(score);
        //}
    }
}