a solution for http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0110

alphametic.rb

def alphametic(input)
  candidate = (input =~ /[\+=]X/ or input =~ /^X/) ? 1..9 : 0..9
  candidate.find {|i| eval(input.gsub('X', i.to_s).sub('=', '==')) } || "NA"
end

if __FILE__ == $0
  while line = gets
    puts alphametic(line.chomp)
  end
end