#coding=UTF-8
#並び換えが出来るのなら楽なはず

S=input()
hindo={'t':0,'r':0,'e':0}

for moji in S:
    hindo[moji]= (hindo[moji] if moji in hindo else 0)+1

print(min(hindo['t'],hindo['r'],hindo['e']//2))#eは2個必要なことに注意