using System;
using System.Linq;
static class A
{
    public static int Main()
    {
        var s=Console.ReadLine();
        int ans=Math.Min(s.Count(x=>x=='r'), s.Count(x=>x=='t'));
        ans=Math.Min(ans, s.Count(x=>x=='e')/2);
        Console.WriteLine(ans);
        return 0;
    }
}