<?php

fscanf(STDIN, "%s", $all);

$str = str_split($all);

$word_t = 0;
$word_r = 0;
$word_e = 0;

foreach($str as $word){
       if($word === "t"){
          $word_t ++;
       }else if($word === "r"){
          $word_r ++;
       }else if($word === "e"){
          $word_e ++;
       }
}

if($word_t > $word_r){
    $word_e_same = $word_r * 2;
}else{
    $word_e_same = $word_t * 2;
}


if($word_t >= 1 && $word_r >= 1 && $word_e >= $word_e_same && $word_t > $word_r){
    echo $word_r;
}else if($word_t >= 1 && $word_r >= 1 && $word_e >= $word_e_same && $word_t < $word_r){
    echo $word_t;
}else if($word_t >= 1 && $word_r >= 1 && $word_e >= $word_e_same && $word_t == $word_r){
    echo $word_t;
}else{
    echo 0;
}