<?php
fscanf(STDIN, "%s", $input);

$arr = str_split($input);

$t=0;
$r=0;
$e=0;

foreach($arr as $val){
    if($val == "t") $t++;
    if($val == "r") $r++;
    if($val == "e") $e++;
}

if($t == 0 || $r == 0 || $e == 0 || $e == 1) $res = 0;

$min = min($t, $r);
if($e>=$min*2) $res = $e/2;


echo $res;
echo "\n";


?>