processes.rb

mem, *processes = ARGV.map(&:to_i)
rates = processes.map{|i| Rational(1, i)}

def memory_for_second(second, processes)
  processes.reduce(0) {|sum, process| sum + (second / process)}
end

def minimum_second(mem, rates)
  (mem / rates.reduce(&:+) ).floor
end

current_tick = minimum_second(mem, rates)
used_memory = memory_for_second(current_tick, processes)
while used_memory < mem
  current_tick += 1
  used_memory = memory_for_second(current_tick, processes)
end

puts "Process count: #{processes.size}"
puts "Total memory: #{mem}"
puts "Memory used up: #{current_tick}s"