using System;
using System.Collections.Generic;
public class Dinglemouse
{
    static string origString = "";
    public static HashSet<string> TrueBananas(string s)
    {
        var result = new HashSet<string>();
        string pure = s.Replace("-", String.Empty);
        if (pure.Length == 6)
        {
            if (pure == "banana")
                result.Add(s);
        }
        else if (pure.Length < 6)
        {
            for (int i = 0; i < s.Length && s[i] == '-'; i++)
            {
                result.UnionWith(
                    TrueBananas(
                        ReplaceByIndex(s, i, origString[i])
                    )
                );
            }
        }
        return result;
    }
    public static HashSet<string> Bananas(string s)
    {
        origString = s;
        string mask = "";
        foreach (char i in s)
            mask += '-';
        var result = new HashSet<string>();
        result.UnionWith(TrueBananas(mask));
        return result;
    }
    static string ReplaceByIndex(string oldStr, int index, char newChar)
    {
        string temp = "";
        for (int i = 0; i < oldStr.Length; i++)
            temp += (index == i ? newChar : oldStr[i]);
        return temp;
    }
}