class Yukicoder
  def initialize
    n = gets.chomp.to_i

    sum = 0

    n.times do
      c, d = gets.chomp.split(' ').map(&:to_i)

      sum += (c/2 + c%2) * d
      sum %= (10 ** 9 + 7)
    end

    puts sum
  end
end

Yukicoder.new