<?php

$str_arr = array();

while(( $S = fgetc( STDIN ) )) {
	if ($S=='t'){
        $str_arr['t'] += 1;
	}else if($S=='r'){
		$str_arr['r'] += 1;
	}else if($S=='e'){
		$str_arr['e'] += 1;
	}
}

$S = "";
$min = 0;

if ($str_arr['r']>=$str_arr['t']){
	$min = $str_arr["t"];
}else{
	$min = $str_arr["r"];
}

$e_min = floor( $str_arr['e'] / 2 );

$ans = 0;

if ($min>=$e_min){
	$ans = $e_min;
}else{
	$ans = $min;
}

echo $ans . "\n";