public static void Main()
Console.WriteLine("longest");
string b1 = Console.ReadLine();
int[] alphabet = new int[26];
for (int i = 1; i < b1.Length; i++)
for (int j = 0; (i + j) < b1.Length; j++)
string str = b1.Substring(i, j + 1);
for (int p = 0; p < 26; p++)