print((function (s,t,r,e)
	s:gsub(".", function (c)
		if c == "t" then t = t + 1
		elseif c == "r" then r = r + 1
		elseif c == "e" then e = e + 1
		end
	end)
	e = bit.rshift(e, 1)
	return math.min(t,r,e)
end)(io.stdin:read("*l"),0,0,0))