using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly string Pattern = "yuki";

    public void Solve()
    {
        int N = Reader.Int();
        var S = Reader.String();
        int[] count = new int[256];
        foreach (char c in S) count[c]++;
        int ans = 0;
        while (MakeOne(count)) ans++;

        Console.WriteLine(ans);
    }

    bool MakeOne(int[] count)
    {
        string s = "";
        for (int len = 0; len <= Pattern.Length + 1; len++)
        {
            string patternPrefix = Pattern.Substring(0, Math.Min(s.Length + 1, Pattern.Length));
            for (char c = 'a'; c <= 'z'; c++)
                if (count[c] > 0 && (s + c).CompareTo(patternPrefix) >= 0)
                {
                    count[c]--;
                    s += c;
                    if (s.CompareTo(Pattern) > 0) return true;
                    break;
                }
        }
        return false;
    }
}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}