# Alchemical Reduction drill

function reduce(x::Char, y::Char)
  if (x == lowercase(y)) || (y == lowercase(x))
    return ""
  else
    return string(x,y)
  end
end

function reduce(z::AbstractString, n::Int64)
  for i = 2:n
    x = z[i-1]
    y = z[i]
    new = reduce(x, y)

    if length(new) == 0
      return string(z[1:(i-2)], z[(i+1):end]), 1
    end
  end

  return z, -1
end

function main(z::AbstractString)
  while true
    n = length(z)
    z, flag = reduce(z, n)
    if flag == -1; return z; end
  end
end