class Total
    attr_reader :n

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

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

    def dataoutput
        puts (1..@n).inject(:+)
    end

    def run
        datainput
        dataoutput
    end
end

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