#!/usr/bin/env ruby

class Firewall
  class Layer
    def initialize(range)
      @period = (range - 1) * 2
    end

    def will_capture_at?(time)
      return time % @period == 0
    end
  end

  def initialize
    @layers = []
  end

  def add_layer!(depth, range)
    @layers[depth] = Layer.new(range)
  end

  def will_capture_at?(time)
    (0...@layers.length).each do |i|
      next if @layers[i].nil?
      return true if @layers[i].will_capture_at?(time + i)
    end
    return false
  end
end


input = $stdin.readlines.map(&:chomp).map{|l|l.split(': ').map(&:to_i)}

firewall = Firewall.new
input.each do |line|
  firewall.add_layer!(line[0], line[1])
end

delay = 0
delay += 1 while firewall.will_capture_at?(delay)

puts delay