[백준] 4948번 : 베르트랑 공준 - C#

https://www.acmicpc.net/problem/4948

using System;

class Program
{
    static void Main() {
        while(true){
            string s=Console.ReadLine();
            int n=int.Parse(s);
            if(n==0) break;
            int count=0;
            int cnt=0;
            for(int i=n+1;i<=2*n;i++){
                for(int j=2;j<=(int)Math.Sqrt(i);j++){
                    if(i%j==0){
                        cnt=1;
                        break;
                    }
                }
                if(cnt==0) count++;
                cnt=0;
            }
            Console.WriteLine(count);
        }
    }
}