using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var s = ReadLine();

        var c0 = 0;
        var c1 = 0;
        var c2 = 0;
        var o0 = 0;
        var o1 = 0;
        var o2 = 0;
        var n0 = 0;
        var n1 = 0;
        var n2 = 0;
        for (var i = 0; i < n; ++i)
        {
            if (s[i * 3] == 'c') ++c0;
            if (s[i * 3] == 'o') ++o0;
            if (s[i * 3] == 'n') ++n0;
            if (s[i * 3 + 1] == 'c') ++c1;
            if (s[i * 3 + 1] == 'o') ++o1;
            if (s[i * 3 + 1] == 'n') ++n1;
            if (s[i * 3 + 2] == 'c') ++c2;
            if (s[i * 3 + 2] == 'o') ++o2;
            if (s[i * 3 + 2] == 'n') ++n2;
        }
        var con = Math.Min(c0, Math.Min(o1, n2));
        var onc = Math.Min(o0, Math.Min(n1, c2));
        var nco = Math.Min(n0, Math.Min(c1, o2));
        var res = con;
        res = Math.Max(res, Math.Min(n - 1, con + onc + nco));
        WriteLine(res);
    }
}