using System;

Console.Write("please write non-negative integer:");    

int kelet= int.Parse(Console.ReadLine());

int maxnum=0;

while (kelet>0&&kelet<=99){

    kelet= int.Parse(Console.ReadLine());

    int tens = kelet / 10;  

    int ones = kelet % 10;

    if (ones != 0 && (tens % ones) == 0 || tens != 0 && (ones % tens) == 0){

​

if (kelet>maxnum){

    maxnum=kelet;

​

    }

}

  if (maxnum > 0)

        {

            Console.WriteLine(maxnum);

  }

}

​