[백준] 2033번 : 반올림 - C#

https://www.acmicpc.net/problem/2033

using System;

class Program
{
    static void Main() {
        string s=Console.ReadLine();
        int n=int.Parse(s);
        int t=1;
        int num=n;
        while(n>9){
            int a=n%10;
            if(a>=5){
                num+=(10-a)*t;
                n+=10;
            }
            else num-=a*t;
            t*=10;
            n/=10;
        }
        Console.Write(num);
    }
}