class CountUpTrees
    attr_reader :s

    def initialize(s: "")
        @s = s
    end

    def cause
        begin
            @s = gets.chomp
        rescue
            
        end
    end

    def countuptrees(target)
        str = "tree".split("").uniq
        cnt = str.each.map { |c| target.count(c) }
        cnt[2] /= 2
        cnt.min
    end

    def result
        puts countuptrees(@s)
    end

    def run
        cause
        result
    end
end

if $0 == __FILE__
    CountUpTrees.new.run
end