using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        var s = Console.ReadLine().Trim();
        getAns(n, s);
    }
    static void getAns(int n, string s)
    {
        s = s.Replace("CPCTF", "a");
        var m = s.Length;
        var ans = (n - m) / 4;
        var start = 0;
        while (true)
        {
            var p = s.IndexOf("CPCTCPC", start);
            if (p == -1) break;
            ans++;
            var np = p + 7;
            if (np + 7 > m) break;
            p = np;
        }
        Console.WriteLine(ans);
    }
}