p = 50
puts $<.count { |i|
  p = (p + (i[0] == ?R ? 1 : -1) * i[1..].to_i) % 100
  p.zero?
}

p = 50
puts $<.sum { |i|
  r = i[1..].to_i
  d = i[0] == ?R ? 1 : -1
  c = (r + p * d % 100) / 100
  p = (p + d * r) % 100
  c
}

puts $<.read.split(',').sum { |r|
  a, b = r.split('-').map(&:to_i)
  (a..b).sum { |n|
    n.to_s =~ /^(.+)\1$/ ? n : 0
  }
}

puts $<.read.split(',').sum { |r|
  a, b = r.split('-').map(&:to_i)
  (a..b).sum { |n|
    n.to_s =~ /^(.+)\1+$/ ? n : 0
  }
}

puts $<.sum { |l|
  l.chars.combination(2).map { |a, b| (a + b).to_i }.max
}

puts $<.read.split.sum { |b|
  [].tap { |s|
    x = b.size - 12
    b.each_char { |c|
      s.pop && x -= 1 while x > 0 && s.last&.<(c)
      s << c
    }
  }.take(12).join.to_i
}

R = {}
$<.each_with_index do |l, i|
  l.chars.each_with_index do |c, j|
    R[i + j*1i] = true if c == ?@
  end
end

N = [-1-1i, -1+0i, -1+1i, 0-1i,   0+1i,  1-1i, 1+0i, 1+1i]
p R.keys.count { |z| N.count { |d| R[z + d] } < 4 }

R = {}
$<.each_with_index do |l, i|
  l.chars.each_with_index do |c, j|
    R[i + j*1i] = true if c == ?@
  end
end

N = [-1-1i, -1+0i, -1+1i, 0-1i,   0+1i,  1-1i, 1+0i, 1+1i]
p R.size.tap { nil while R.reject! { |z, _| N.count { |d| R[z + d] } < 4 }} - R.size

r, i = $<.read.split /\n\n/
f = r.scan(/(\d+)-(\d+)/).map { |a, b| a.to_i..b.to_i }
p i.lines.map(&:to_i).count { |y| f.any? { _1 === y } }

p $<.read
    .split(/\n\n/)[0]
    .scan(/(\d+)-(\d+)/)
    .map { _1.map(&:to_i) }
    .sort
    .reduce([]) { |m, (a, b)|
      if !m[0] || m[-1][1] < a - 1
        m << [a, b]
      else
        m[-1][1] = [m[-1][1], b].max
        m
      end
    }
    .sum { |a, b| b - a + 1 }