class MillionDies
    attr_reader :n

    def initialize(n: 0)
        @n = n
    end

    def cause
        begin
            @n = Integer(gets.chomp)
        rescue
            
        end
    end

    def result
        puts (@n % 2 == 0)? (@n * 3.5).to_i : (@n * 3.5)
    end

    def run
        cause
        result
    end
end

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