#ciqprocon

2112.rb

hands = %w(G C P G)
puts hands[(hands.index(gets.chomp)||0) + 1]

2113.rb

n = gets.chomp.to_i
p (Math.log(2*n+1)/Math.log(3)).ceil

2114.rb

class RamenMap
  Tile = Struct.new(:word, :next)

  class << self
    def parse(data)
      map_data = {}
      data.each.with_index do |line, y|
        line.each.with_index do |word, x|
          map_data[[x, y]] = Tile.new(word, next_point(x, y))
        end
      end
      map_data.update(map_data) do |_, tile|
        tile.next.select!{|next_point| map_data.key?(next_point) }
        tile
      end
    end

    def next_point(x, y)
      [[0, 1], [1, 0], [0, -1], [-1, 0]].map do |mx, my|
        [x + mx, y + my]
      end
    end
  end
end

map_data = $stdin.read.split(?\n).map{|str| str.each_char.to_a }
ramen_map = RamenMap.parse(map_data)
result =
  ramen_map.keys
    .select{|point|   ramen_map[point].word == 'A' }
    .flat_map{|point| ramen_map[point].next }
    .select{|point|   ramen_map[point].word == 'M' }
    .flat_map{|point| ramen_map[point].next }
    .select{|point|   ramen_map[point].word == 'N' }
    .flat_map{|point| ramen_map[point].next }
    .select{|point|   ramen_map[point].word == 'E' }
    .flat_map{|point| ramen_map[point].next }
    .any?{|point|     ramen_map[point].word == 'M' }
puts result ? 'yes' : 'no'

2115.rb

p [*1..gets.chomp.to_i]
    .repeated_combination(2)
    .group_by{|x,y| x ** 3 + y ** 3 }
    .select{|k,v| v.size > 1 }
    .sort.last.last.last
    .map{|i| i ** 3 }
    .inject(:+)