using System;
public class Test
{
public static void Main()
{
// your code goes here
string a = null;
string b = null;
var result = string.Format("{0}/{1}", a, b);
Console.WriteLine(result);
Console.WriteLine(result == null);
}
}
dXNpbmcgU3lzdGVtOwoKcHVibGljIGNsYXNzIFRlc3QKewoJcHVibGljIHN0YXRpYyB2b2lkIE1haW4oKQoJewoJCS8vIHlvdXIgY29kZSBnb2VzIGhlcmUKCQlzdHJpbmcgYSA9IG51bGw7CgkJc3RyaW5nIGIgPSBudWxsOwoJCQoJCXZhciByZXN1bHQgPSBzdHJpbmcuRm9ybWF0KCJ7MH0vezF9IiwgYSwgYik7CgkJCgkJQ29uc29sZS5Xcml0ZUxpbmUocmVzdWx0KTsKCQlDb25zb2xlLldyaXRlTGluZShyZXN1bHQgPT0gbnVsbCk7Cgl9Cn0=