x=list(input())
count=0
y=[]
for i in x:
    y.append(i)
    if "t" in y and "r" in y and y.count("e")>1:
        count+=1
        y.remove("t")
        y.remove("r")
        y.remove("e")
        y.remove("e")
    else:
        continue
print(count)